diff --git a/Cargo.lock b/Cargo.lock
index 9fa6e1d51d2..25b43227d6f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4008,10 +4008,14 @@ dependencies = [
 name = "rustc_macros"
 version = "0.1.0"
 dependencies = [
+ "annotate-snippets",
+ "fluent-bundle",
+ "fluent-syntax",
  "proc-macro2",
  "quote",
  "syn",
  "synstructure",
+ "unic-langid",
 ]
 
 [[package]]
diff --git a/compiler/rustc_error_messages/src/lib.rs b/compiler/rustc_error_messages/src/lib.rs
index e1e0ed7222d..7faf14a2472 100644
--- a/compiler/rustc_error_messages/src/lib.rs
+++ b/compiler/rustc_error_messages/src/lib.rs
@@ -6,7 +6,7 @@
 use fluent_bundle::FluentResource;
 use fluent_syntax::parser::ParserError;
 use rustc_data_structures::sync::Lrc;
-use rustc_macros::{Decodable, Encodable};
+use rustc_macros::{fluent_messages, Decodable, Encodable};
 use rustc_span::Span;
 use std::borrow::Cow;
 use std::error::Error;
@@ -29,8 +29,13 @@
 pub use fluent_bundle::{FluentArgs, FluentError, FluentValue};
 pub use unic_langid::{langid, LanguageIdentifier};
 
-pub static DEFAULT_LOCALE_RESOURCES: &'static [&'static str] =
-    &[include_str!("../locales/en-US/typeck.ftl"), include_str!("../locales/en-US/parser.ftl")];
+// Generates `DEFAULT_LOCALE_RESOURCES` static and `fluent_generated` module.
+fluent_messages! {
+    parser => "../locales/en-US/parser.ftl",
+    typeck => "../locales/en-US/typeck.ftl",
+}
+
+pub use fluent_generated::{self as fluent, DEFAULT_LOCALE_RESOURCES};
 
 pub type FluentBundle = fluent_bundle::bundle::FluentBundle<FluentResource, IntlLangMemoizer>;
 
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index d2f50d5df54..5b9b65da343 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -31,8 +31,8 @@
 use rustc_data_structures::sync::{self, Lock, Lrc};
 use rustc_data_structures::AtomicRef;
 pub use rustc_error_messages::{
-    fallback_fluent_bundle, fluent_bundle, DiagnosticMessage, FluentBundle, LanguageIdentifier,
-    LazyFallbackBundle, MultiSpan, SpanLabel, DEFAULT_LOCALE_RESOURCES,
+    fallback_fluent_bundle, fluent, fluent_bundle, DiagnosticMessage, FluentBundle,
+    LanguageIdentifier, LazyFallbackBundle, MultiSpan, SpanLabel, DEFAULT_LOCALE_RESOURCES,
 };
 pub use rustc_lint_defs::{pluralize, Applicability};
 use rustc_span::source_map::SourceMap;
diff --git a/compiler/rustc_macros/Cargo.toml b/compiler/rustc_macros/Cargo.toml
index a9192be4d6e..25b3aadc1c5 100644
--- a/compiler/rustc_macros/Cargo.toml
+++ b/compiler/rustc_macros/Cargo.toml
@@ -7,7 +7,11 @@ edition = "2021"
 proc-macro = true
 
 [dependencies]
+annotate-snippets = "0.8.0"
+fluent-bundle = "0.15.2"
+fluent-syntax = "0.11"
 synstructure = "0.12.1"
 syn = { version = "1", features = ["full"] }
 proc-macro2 = "1"
 quote = "1"
+unic-langid = { version = "0.9.0", features = ["macros"] }
diff --git a/compiler/rustc_macros/src/diagnostics/fluent.rs b/compiler/rustc_macros/src/diagnostics/fluent.rs
new file mode 100644
index 00000000000..8523d7fa9f9
--- /dev/null
+++ b/compiler/rustc_macros/src/diagnostics/fluent.rs
@@ -0,0 +1,254 @@
+use annotate_snippets::{
+    display_list::DisplayList,
+    snippet::{Annotation, AnnotationType, Slice, Snippet, SourceAnnotation},
+};
+use fluent_bundle::{FluentBundle, FluentError, FluentResource};
+use fluent_syntax::{
+    ast::{Attribute, Entry, Identifier, Message},
+    parser::ParserError,
+};
+use proc_macro::{Diagnostic, Level, Span};
+use proc_macro2::TokenStream;
+use quote::quote;
+use std::{
+    collections::HashMap,
+    fs::File,
+    io::Read,
+    path::{Path, PathBuf},
+};
+use syn::{
+    parse::{Parse, ParseStream},
+    parse_macro_input,
+    punctuated::Punctuated,
+    token, Ident, LitStr, Result,
+};
+use unic_langid::langid;
+
+struct Resource {
+    ident: Ident,
+    #[allow(dead_code)]
+    fat_arrow_token: token::FatArrow,
+    resource: LitStr,
+}
+
+impl Parse for Resource {
+    fn parse(input: ParseStream<'_>) -> Result<Self> {
+        Ok(Resource {
+            ident: input.parse()?,
+            fat_arrow_token: input.parse()?,
+            resource: input.parse()?,
+        })
+    }
+}
+
+struct Resources(Punctuated<Resource, token::Comma>);
+
+impl Parse for Resources {
+    fn parse(input: ParseStream<'_>) -> Result<Self> {
+        let mut resources = Punctuated::new();
+        loop {
+            if input.is_empty() || input.peek(token::Brace) {
+                break;
+            }
+            let value = input.parse()?;
+            resources.push_value(value);
+            if !input.peek(token::Comma) {
+                break;
+            }
+            let punct = input.parse()?;
+            resources.push_punct(punct);
+        }
+        Ok(Resources(resources))
+    }
+}
+
+/// Helper function for returning an absolute path for macro-invocation relative file paths.
+///
+/// If the input is already absolute, then the input is returned. If the input is not absolute,
+/// then it is appended to the directory containing the source file with this macro invocation.
+fn invocation_relative_path_to_absolute(span: Span, path: &str) -> PathBuf {
+    let path = Path::new(path);
+    if path.is_absolute() {
+        path.to_path_buf()
+    } else {
+        // `/a/b/c/foo/bar.rs` contains the current macro invocation
+        let mut source_file_path = span.source_file().path();
+        // `/a/b/c/foo/`
+        source_file_path.pop();
+        // `/a/b/c/foo/../locales/en-US/example.ftl`
+        source_file_path.push(path);
+        source_file_path
+    }
+}
+
+/// See [rustc_macros::fluent_messages].
+pub(crate) fn fluent_messages(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let resources = parse_macro_input!(input as Resources);
+
+    // Cannot iterate over individual messages in a bundle, so do that using the
+    // `FluentResource` instead. Construct a bundle anyway to find out if there are conflicting
+    // messages in the resources.
+    let mut bundle = FluentBundle::new(vec![langid!("en-US")]);
+
+    // Map of Fluent identifiers to the `Span` of the resource that defined them, used for better
+    // diagnostics.
+    let mut previous_defns = HashMap::new();
+
+    let mut includes = TokenStream::new();
+    let mut generated = TokenStream::new();
+    for res in resources.0 {
+        let ident_span = res.ident.span().unwrap();
+        let path_span = res.resource.span().unwrap();
+
+        let relative_ftl_path = res.resource.value();
+        let absolute_ftl_path =
+            invocation_relative_path_to_absolute(ident_span, &relative_ftl_path);
+        // As this macro also outputs an `include_str!` for this file, the macro will always be
+        // re-executed when the file changes.
+        let mut resource_file = match File::open(absolute_ftl_path) {
+            Ok(resource_file) => resource_file,
+            Err(e) => {
+                Diagnostic::spanned(path_span, Level::Error, "could not open Fluent resource")
+                    .note(e.to_string())
+                    .emit();
+                continue;
+            }
+        };
+        let mut resource_contents = String::new();
+        if let Err(e) = resource_file.read_to_string(&mut resource_contents) {
+            Diagnostic::spanned(path_span, Level::Error, "could not read Fluent resource")
+                .note(e.to_string())
+                .emit();
+            continue;
+        }
+        let resource = match FluentResource::try_new(resource_contents) {
+            Ok(resource) => resource,
+            Err((this, errs)) => {
+                Diagnostic::spanned(path_span, Level::Error, "could not parse Fluent resource")
+                    .help("see additional errors emitted")
+                    .emit();
+                for ParserError { pos, slice: _, kind } in errs {
+                    let mut err = kind.to_string();
+                    // Entirely unnecessary string modification so that the error message starts
+                    // with a lowercase as rustc errors do.
+                    err.replace_range(
+                        0..1,
+                        &err.chars().next().unwrap().to_lowercase().to_string(),
+                    );
+
+                    let line_starts: Vec<usize> = std::iter::once(0)
+                        .chain(
+                            this.source()
+                                .char_indices()
+                                .filter_map(|(i, c)| Some(i + 1).filter(|_| c == '\n')),
+                        )
+                        .collect();
+                    let line_start = line_starts
+                        .iter()
+                        .enumerate()
+                        .map(|(line, idx)| (line + 1, idx))
+                        .filter(|(_, idx)| **idx <= pos.start)
+                        .last()
+                        .unwrap()
+                        .0;
+
+                    let snippet = Snippet {
+                        title: Some(Annotation {
+                            label: Some(&err),
+                            id: None,
+                            annotation_type: AnnotationType::Error,
+                        }),
+                        footer: vec![],
+                        slices: vec![Slice {
+                            source: this.source(),
+                            line_start,
+                            origin: Some(&relative_ftl_path),
+                            fold: true,
+                            annotations: vec![SourceAnnotation {
+                                label: "",
+                                annotation_type: AnnotationType::Error,
+                                range: (pos.start, pos.end - 1),
+                            }],
+                        }],
+                        opt: Default::default(),
+                    };
+                    let dl = DisplayList::from(snippet);
+                    eprintln!("{}\n", dl);
+                }
+                continue;
+            }
+        };
+
+        let mut constants = TokenStream::new();
+        for entry in resource.entries() {
+            let span = res.ident.span();
+            if let Entry::Message(Message { id: Identifier { name }, attributes, .. }) = entry {
+                let _ = previous_defns.entry(name.to_string()).or_insert(ident_span);
+
+                // `typeck-foo-bar` => `foo_bar`
+                let snake_name = Ident::new(
+                    &name.replace(&format!("{}-", res.ident), "").replace("-", "_"),
+                    span,
+                );
+                constants.extend(quote! {
+                    pub const #snake_name: crate::DiagnosticMessage =
+                        crate::DiagnosticMessage::FluentIdentifier(
+                            std::borrow::Cow::Borrowed(#name),
+                            None
+                        );
+                });
+
+                for Attribute { id: Identifier { name: attr_name }, .. } in attributes {
+                    let attr_snake_name = attr_name.replace("-", "_");
+                    let snake_name = Ident::new(&format!("{snake_name}_{attr_snake_name}"), span);
+                    constants.extend(quote! {
+                        pub const #snake_name: crate::DiagnosticMessage =
+                            crate::DiagnosticMessage::FluentIdentifier(
+                                std::borrow::Cow::Borrowed(#name),
+                                Some(std::borrow::Cow::Borrowed(#attr_name))
+                            );
+                    });
+                }
+            }
+        }
+
+        if let Err(errs) = bundle.add_resource(resource) {
+            for e in errs {
+                match e {
+                    FluentError::Overriding { kind, id } => {
+                        Diagnostic::spanned(
+                            ident_span,
+                            Level::Error,
+                            format!("overrides existing {}: `{}`", kind, id),
+                        )
+                        .span_help(previous_defns[&id], "previously defined in this resource")
+                        .emit();
+                    }
+                    FluentError::ResolverError(_) | FluentError::ParserError(_) => unreachable!(),
+                }
+            }
+        }
+
+        includes.extend(quote! { include_str!(#relative_ftl_path), });
+
+        let ident = res.ident;
+        generated.extend(quote! {
+            pub mod #ident {
+                #constants
+            }
+        });
+    }
+
+    quote! {
+        #[allow(non_upper_case_globals)]
+        #[doc(hidden)]
+        pub mod fluent_generated {
+            pub static DEFAULT_LOCALE_RESOURCES: &'static [&'static str] = &[
+                #includes
+            ];
+
+            #generated
+        }
+    }
+    .into()
+}
diff --git a/compiler/rustc_macros/src/diagnostics/mod.rs b/compiler/rustc_macros/src/diagnostics/mod.rs
index ccd3880057b..69573d904d4 100644
--- a/compiler/rustc_macros/src/diagnostics/mod.rs
+++ b/compiler/rustc_macros/src/diagnostics/mod.rs
@@ -1,9 +1,11 @@
 mod diagnostic;
 mod error;
+mod fluent;
 mod subdiagnostic;
 mod utils;
 
 use diagnostic::SessionDiagnosticDerive;
+pub(crate) use fluent::fluent_messages;
 use proc_macro2::TokenStream;
 use quote::format_ident;
 use subdiagnostic::SessionSubdiagnosticDerive;
diff --git a/compiler/rustc_macros/src/lib.rs b/compiler/rustc_macros/src/lib.rs
index 0baebdb7130..7c8e3c6d140 100644
--- a/compiler/rustc_macros/src/lib.rs
+++ b/compiler/rustc_macros/src/lib.rs
@@ -2,6 +2,7 @@
 #![feature(let_else)]
 #![feature(never_type)]
 #![feature(proc_macro_diagnostic)]
+#![feature(proc_macro_span)]
 #![allow(rustc::default_hash_types)]
 #![recursion_limit = "128"]
 
@@ -49,6 +50,64 @@ pub fn newtype_index(input: TokenStream) -> TokenStream {
     newtype::newtype(input)
 }
 
+/// Implements the `fluent_messages` macro, which performs compile-time validation of the
+/// compiler's Fluent resources (i.e. that the resources parse and don't multiply define the same
+/// messages) and generates constants that make using those messages in diagnostics more ergonomic.
+///
+/// For example, given the following invocation of the macro..
+///
+/// ```ignore (rust)
+/// fluent_messages! {
+///     typeck => "./typeck.ftl",
+/// }
+/// ```
+/// ..where `typeck.ftl` has the following contents..
+///
+/// ```fluent
+/// typeck-field-multiply-specified-in-initializer =
+///     field `{$ident}` specified more than once
+///     .label = used more than once
+///     .label-previous-use = first use of `{$ident}`
+/// ```
+/// ...then the macro parse the Fluent resource, emitting a diagnostic if it fails to do so, and
+/// will generate the following code:
+///
+/// ```ignore (rust)
+/// pub static DEFAULT_LOCALE_RESOURCES: &'static [&'static str] = &[
+///     include_str!("./typeck.ftl"),
+/// ];
+///
+/// mod fluent_generated {
+///     mod typeck {
+///         pub const field_multiply_specified_in_initializer: DiagnosticMessage =
+///             DiagnosticMessage::fluent("typeck-field-multiply-specified-in-initializer");
+///         pub const field_multiply_specified_in_initializer_label_previous_use: DiagnosticMessage =
+///             DiagnosticMessage::fluent_attr(
+///                 "typeck-field-multiply-specified-in-initializer",
+///                 "previous-use-label"
+///             );
+///     }
+/// }
+/// ```
+/// When emitting a diagnostic, the generated constants can be used as follows:
+///
+/// ```ignore (rust)
+/// let mut err = sess.struct_span_err(
+///     span,
+///     fluent::typeck::field_multiply_specified_in_initializer
+/// );
+/// err.span_default_label(span);
+/// err.span_label(
+///     previous_use_span,
+///     fluent::typeck::field_multiply_specified_in_initializer_label_previous_use
+/// );
+/// err.emit();
+/// ```
+#[proc_macro]
+pub fn fluent_messages(input: TokenStream) -> TokenStream {
+    diagnostics::fluent_messages(input)
+}
+
 decl_derive!([HashStable, attributes(stable_hasher)] => hash_stable::hash_stable_derive);
 decl_derive!(
     [HashStable_Generic, attributes(stable_hasher)] =>
diff --git a/src/test/ui-fulldeps/fluent-messages/duplicate-a.ftl b/src/test/ui-fulldeps/fluent-messages/duplicate-a.ftl
new file mode 100644
index 00000000000..fd9976b5a41
--- /dev/null
+++ b/src/test/ui-fulldeps/fluent-messages/duplicate-a.ftl
@@ -0,0 +1 @@
+key = Value
diff --git a/src/test/ui-fulldeps/fluent-messages/duplicate-b.ftl b/src/test/ui-fulldeps/fluent-messages/duplicate-b.ftl
new file mode 100644
index 00000000000..fd9976b5a41
--- /dev/null
+++ b/src/test/ui-fulldeps/fluent-messages/duplicate-b.ftl
@@ -0,0 +1 @@
+key = Value
diff --git a/src/test/ui-fulldeps/fluent-messages/missing-message.ftl b/src/test/ui-fulldeps/fluent-messages/missing-message.ftl
new file mode 100644
index 00000000000..372b1a2e453
--- /dev/null
+++ b/src/test/ui-fulldeps/fluent-messages/missing-message.ftl
@@ -0,0 +1 @@
+missing-message = 
diff --git a/src/test/ui-fulldeps/fluent-messages/test.rs b/src/test/ui-fulldeps/fluent-messages/test.rs
new file mode 100644
index 00000000000..b05d3d08ccb
--- /dev/null
+++ b/src/test/ui-fulldeps/fluent-messages/test.rs
@@ -0,0 +1,60 @@
+// normalize-stderr-test "note.*" -> "note: os-specific message"
+
+#![feature(rustc_private)]
+#![crate_type = "lib"]
+
+extern crate rustc_macros;
+use rustc_macros::fluent_messages;
+
+/// Copy of the relevant `DiagnosticMessage` variant constructed by `fluent_messages` as it
+/// expects `crate::DiagnosticMessage` to exist.
+pub enum DiagnosticMessage {
+    FluentIdentifier(std::borrow::Cow<'static, str>, Option<std::borrow::Cow<'static, str>>),
+}
+
+mod missing_absolute {
+    use super::fluent_messages;
+
+    fluent_messages! {
+        missing_absolute => "/definitely_does_not_exist.ftl",
+//~^ ERROR could not open Fluent resource
+    }
+}
+
+mod missing_relative {
+    use super::fluent_messages;
+
+    fluent_messages! {
+        missing_relative => "../definitely_does_not_exist.ftl",
+//~^ ERROR could not open Fluent resource
+    }
+}
+
+mod missing_message {
+    use super::fluent_messages;
+
+    fluent_messages! {
+        missing_message => "./missing-message.ftl",
+//~^ ERROR could not parse Fluent resource
+    }
+}
+
+mod duplicate {
+    use super::fluent_messages;
+
+    fluent_messages! {
+        a => "./duplicate-a.ftl",
+        b => "./duplicate-b.ftl",
+//~^ ERROR overrides existing message: `key`
+    }
+}
+
+mod valid {
+    use super::fluent_messages;
+
+    fluent_messages! {
+        valid => "./valid.ftl",
+    }
+
+    use self::fluent_generated::{DEFAULT_LOCALE_RESOURCES, valid::valid};
+}
diff --git a/src/test/ui-fulldeps/fluent-messages/test.stderr b/src/test/ui-fulldeps/fluent-messages/test.stderr
new file mode 100644
index 00000000000..f88d09bee6e
--- /dev/null
+++ b/src/test/ui-fulldeps/fluent-messages/test.stderr
@@ -0,0 +1,45 @@
+error: could not open Fluent resource
+  --> $DIR/test.rs:19:29
+   |
+LL |         missing_absolute => "/definitely_does_not_exist.ftl",
+   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: os-specific message
+
+error: could not open Fluent resource
+  --> $DIR/test.rs:28:29
+   |
+LL |         missing_relative => "../definitely_does_not_exist.ftl",
+   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: os-specific message
+
+error: could not parse Fluent resource
+  --> $DIR/test.rs:37:28
+   |
+LL |         missing_message => "./missing-message.ftl",
+   |                            ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: see additional errors emitted
+
+error: expected a message field for "missing-message"
+ --> ./missing-message.ftl:1:1
+  |
+1 | missing-message = 
+  | ^^^^^^^^^^^^^^^^^^
+  |
+
+error: overrides existing message: `key`
+  --> $DIR/test.rs:47:9
+   |
+LL |         b => "./duplicate-b.ftl",
+   |         ^
+   |
+help: previously defined in this resource
+  --> $DIR/test.rs:46:9
+   |
+LL |         a => "./duplicate-a.ftl",
+   |         ^
+
+error: aborting due to 4 previous errors
+
diff --git a/src/test/ui-fulldeps/fluent-messages/valid.ftl b/src/test/ui-fulldeps/fluent-messages/valid.ftl
new file mode 100644
index 00000000000..0eee4a02b96
--- /dev/null
+++ b/src/test/ui-fulldeps/fluent-messages/valid.ftl
@@ -0,0 +1 @@
+valid = Valid!