diff --git a/dlls/advapi32/advapi32.spec b/dlls/advapi32/advapi32.spec
index fcef859a7c1..d5235c6adb9 100644
--- a/dlls/advapi32/advapi32.spec
+++ b/dlls/advapi32/advapi32.spec
@@ -463,7 +463,7 @@
 # @ stub LsaGetQuotasForAccount
 # @ stub LsaGetRemoteUserName
 @ stub LsaGetSystemAccessAccount
-# @ stub LsaGetUserName
+@ stdcall LsaGetUserName(ptr ptr)
 @ stub LsaICLookupNames
 # @ stub LsaICLookupNamesWithCreds
 @ stub LsaICLookupSids
diff --git a/dlls/advapi32/lsa.c b/dlls/advapi32/lsa.c
index bd3585f8d06..55e42400c6d 100644
--- a/dlls/advapi32/lsa.c
+++ b/dlls/advapi32/lsa.c
@@ -104,6 +104,64 @@ static void* ADVAPI_GetDomainName(unsigned sz, unsigned ofs)
     return ptr;
 }
 
+/******************************************************************************
+ * LsaGetUserName [ADVAPI32.@]
+ *
+ */
+NTSTATUS WINAPI LsaGetUserName(PUNICODE_STRING *user_name, PUNICODE_STRING *domain_name)
+{
+    UNICODE_STRING *user;
+    DWORD user_size;
+
+    user_size = 0;
+    if (GetUserNameW(NULL, &user_size) || GetLastError() != ERROR_INSUFFICIENT_BUFFER)
+       return STATUS_UNSUCCESSFUL;
+
+    user = heap_alloc(sizeof(*user) + user_size * sizeof(WCHAR));
+    if (!user) return STATUS_NO_MEMORY;
+
+    user->Buffer = (WCHAR *)(user + 1);
+    user->MaximumLength = user_size * sizeof(WCHAR);
+    user->Length = user->MaximumLength - sizeof(WCHAR);
+    if (!GetUserNameW(user->Buffer, &user_size))
+    {
+        heap_free(user);
+        return STATUS_UNSUCCESSFUL;
+    }
+
+    if (domain_name)
+    {
+        UNICODE_STRING *domain;
+        WCHAR computer[MAX_COMPUTERNAME_LENGTH + 1];
+        DWORD domain_size;
+
+        domain_size = ARRAY_SIZE(computer);
+        if (!GetComputerNameW(computer, &domain_size))
+        {
+            heap_free(user);
+            return STATUS_UNSUCCESSFUL;
+        }
+
+        domain = heap_alloc(sizeof(*domain) + (domain_size + 1) * sizeof(WCHAR));
+        if (!domain)
+        {
+            heap_free(user);
+            return STATUS_NO_MEMORY;
+        }
+
+        domain->Buffer = (WCHAR *)(domain + 1);
+        domain->Length = domain_size * sizeof(WCHAR);
+        domain->MaximumLength = domain->Length + sizeof(WCHAR);
+        wcscpy(domain->Buffer, computer);
+
+        *domain_name = domain;
+    }
+
+    *user_name = user;
+
+    return STATUS_SUCCESS;
+}
+
 /******************************************************************************
  * LsaAddAccountRights [ADVAPI32.@]
  *
diff --git a/dlls/advapi32/tests/lsa.c b/dlls/advapi32/tests/lsa.c
index 54a8528bc21..f8c822a7de2 100644
--- a/dlls/advapi32/tests/lsa.c
+++ b/dlls/advapi32/tests/lsa.c
@@ -2,6 +2,7 @@
  * Unit tests for lsa functions
  *
  * Copyright (c) 2006 Robert Reif
+ * Copyright (c) 2020 Dmitry Timoshkov
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -38,6 +39,7 @@
 DEFINE_GUID(GUID_NULL,0,0,0,0,0,0,0,0,0,0,0);
 
 static BOOL (WINAPI *pGetSystemPreferredUILanguages)(DWORD, ULONG*, WCHAR*, ULONG*);
+static NTSTATUS (WINAPI *pLsaGetUserName)(PUNICODE_STRING *user, PUNICODE_STRING *domain);
 
 static void test_lsa(void)
 {
@@ -463,13 +465,59 @@ static void test_LsaLookupPrivilegeName(void)
     LsaFreeMemory(name);
 }
 
+static void test_LsaGetUserName(void)
+{
+    NTSTATUS status;
+    BOOL ret;
+    UNICODE_STRING *lsa_user, *lsa_domain;
+    WCHAR user[256], computer[256];
+    DWORD size;
+
+    if (!pLsaGetUserName)
+    {
+        skip("LsaGetUserName is not available on this platform\n");
+        return;
+    }
+
+    size = ARRAY_SIZE(user);
+    ret = GetUserNameW(user, &size);
+    ok(ret, "GetUserName error %u\n", GetLastError());
+
+    size = ARRAY_SIZE(computer);
+    ret = GetComputerNameW(computer, &size);
+    ok(ret, "GetComputerName error %u\n", GetLastError());
+
+    if (0) /* crashes under Windows */
+        status = pLsaGetUserName(NULL, NULL);
+
+    if (0) /* crashes under Windows */
+        status = pLsaGetUserName(NULL, &lsa_domain);
+
+    status = pLsaGetUserName(&lsa_user, NULL);
+    ok(!status, "got %#x\n", status);
+    check_unicode_string(lsa_user, user);
+    LsaFreeMemory(lsa_user);
+
+    status = pLsaGetUserName(&lsa_user, &lsa_domain);
+    ok(!status, "got %#x\n", status);
+    ok(!lstrcmpW(user, lsa_user->Buffer), "%s != %s\n", wine_dbgstr_w(user), wine_dbgstr_wn(lsa_user->Buffer, lsa_user->Length/sizeof(WCHAR)));
+    check_unicode_string(lsa_user, user);
+    check_unicode_string(lsa_domain, computer);
+    LsaFreeMemory(lsa_user);
+    LsaFreeMemory(lsa_domain);
+}
+
 START_TEST(lsa)
 {
-    HMODULE hkernel32 = GetModuleHandleA("kernel32");
+    HMODULE hkernel32 = GetModuleHandleA("kernel32.dll");
+    HMODULE hadvapi32 = GetModuleHandleA("advapi32.dll");
+
     pGetSystemPreferredUILanguages = (void*)GetProcAddress(hkernel32, "GetSystemPreferredUILanguages");
+    pLsaGetUserName = (void *)GetProcAddress(hadvapi32, "LsaGetUserName");
 
     test_lsa();
     test_LsaLookupNames2();
     test_LsaLookupSids();
     test_LsaLookupPrivilegeName();
+    test_LsaGetUserName();
 }