diff --git a/config.sub b/config.sub
index 38f3d037a78..e15a98ae991 100755
--- a/config.sub
+++ b/config.sub
@@ -1749,7 +1749,7 @@ case $os in
 	     | onefs* | tirtos* | phoenix* | fuchsia* | redox* | bme* \
 	     | midnightbsd* | amdhsa* | unleashed* | emscripten* | wasi* \
 	     | nsk* | powerunix* | genode* | zvmoe* | qnx* | emx* | zephyr* \
-	     | fiwix* )
+	     | fiwix* | fennix* )
 		;;
 	# This one is extra strict with allowed versions
 	sco3.2v2 | sco3.2v[4-9]* | sco5v6*)
diff --git a/gcc/config.gcc b/gcc/config.gcc
index 95c91ee02be..2f3e3b006dd 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -825,6 +825,14 @@ case ${target} in
   rust_target_objs="${rust_target_objs} dragonfly-rust.o"
   target_has_targetrustm=yes
   ;;
+*-*-fennix*)
+  tmake_file="t-fennix "
+  gas=yes
+  gnu_ld=yes
+  default_use_cxa_atexit=yes
+  use_gcc_stdint=provide
+  native_system_header_dir=/include
+  ;;
 *-*-freebsd*)
   # This is the generic ELF configuration of FreeBSD.  Later
   # machine-specific sections may refine and add to this
@@ -1981,6 +1989,14 @@ x86_64-*-openbsd*)
 	gas=yes
 	gnu_ld=yes
 	;;
+i[34567]86-*-fennix*)
+	tmake_file="${tmake_file} i386/t-fennix"
+	tm_file="${tm_file} i386/unix.h i386/att.h elfos.h glibc-stdint.h i386/i386elf.h fennix.h"
+	;;
+x86_64-*-fennix*)
+	tmake_file="${tmake_file} i386/t-fennix"
+	tm_file="${tm_file} i386/unix.h i386/att.h elfos.h glibc-stdint.h i386/i386elf.h i386/x86-64.h fennix.h"
+	;;
 i[34567]86-*-linux* | i[34567]86-*-kfreebsd*-gnu | i[34567]86-*-gnu* | i[34567]86-*-kopensolaris*-gnu)
 			# Intel 80386's running GNU/*
 			# with ELF format using glibc 2
diff --git a/gcc/config/fennix.h b/gcc/config/fennix.h
new file mode 100644
index 00000000000..3739abe7983
--- /dev/null
+++ b/gcc/config/fennix.h
@@ -0,0 +1,59 @@
+
+#undef  TARGET_FENNIX
+#define TARGET_FENNIX 1
+
+#undef  LIB_SPEC
+#define LIB_SPEC "-lc"
+
+#undef  CPP_SPEC
+#define CPP_SPEC "%{posix:-D_POSIX_SOURCE} %{pthread:-D_POSIX_THREADS}"
+
+#undef  STARTFILE_SPEC
+#define STARTFILE_SPEC        \
+ "crti.o%s                    \
+  %{!shared:                  \
+    %{!static:                \
+      crtbeginS.o%s Scrt1.o%s \
+    }                         \
+  }                           \
+  %{static:crtbegin.o%s crt1.o%s}"
+
+#undef  ENDFILE_SPEC
+#define ENDFILE_SPEC        \
+ "crtn.o%s                  \
+  %{!shared:                \
+    %{!static:              \
+      crtendS.o%s           \
+    }                       \
+  }                         \
+  %{static:crtend.o%s}"
+
+#undef  STANDARD_STARTFILE_PREFIX
+#define STANDARD_STARTFILE_PREFIX "/lib/"
+
+#undef  LINK_SPEC
+#define LINK_SPEC                       \
+ "%{shared:-shared}                     \
+  %{static:-static}                     \
+  %{!shared:                            \
+    %{!static:                          \
+      %{rdynamic:-export-dynamic}       \
+    }                                   \
+  }                                     \
+  %{!static:                            \
+    %{!dynamic-linker:                  \
+      -dynamic-linker=/lib/ld.so        \
+    }                                   \
+  }                                     \
+  -z max-page-size=4096"
+
+#undef  TARGET_OS_CPP_BUILTINS
+#define TARGET_OS_CPP_BUILTINS()       \
+  do                                   \
+  {                                    \
+      builtin_define("__fennix__");    \
+      builtin_define("__unix__");      \
+      builtin_assert("system=fennix"); \
+      builtin_assert("system=unix");   \
+      builtin_assert("system=posix");  \
+  } while (0);
diff --git a/gcc/config/i386/t-fennix b/gcc/config/i386/t-fennix
new file mode 100644
index 00000000000..8223e63c0c9
--- /dev/null
+++ b/gcc/config/i386/t-fennix
@@ -0,0 +1,2 @@
+MULTILIB_OPTIONS += mno-red-zone
+MULTILIB_DIRNAMES += no-red-zone
diff --git a/libgcc/config.host b/libgcc/config.host
index e75a7af647f..12ecba7be60 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -760,6 +760,14 @@ x86_64-*-dragonfly*)
 	tmake_file="${tmake_file} i386/t-dragonfly i386/t-crtstuff"
 	md_unwind_header=i386/dragonfly-unwind.h
 	;;
+i[34567]86-*-fennix*)
+	extra_parts="$extra_parts crti.o crtn.o crtbegin.o crtend.o crtbeginS.o crtendS.o"
+	tmake_file="$tmake_file i386/t-crtstuff t-crtstuff-pic t-libgcc-pic"
+	;;
+x86_64-*-fennix*)
+	extra_parts="$extra_parts crti.o crtn.o crtbegin.o crtend.o crtbeginS.o crtendS.o"
+	tmake_file="$tmake_file i386/t-crtstuff t-crtstuff-pic t-libgcc-pic"
+	;;
 i[34567]86-*-freebsd*)
 	tmake_file="${tmake_file} i386/t-freebsd i386/t-crtstuff"
 	md_unwind_header=i386/freebsd-unwind.h
diff --git a/libstdc++-v3/crossconfig.m4 b/libstdc++-v3/crossconfig.m4
index b3269cb88e0..de1f886b9a6 100644
--- a/libstdc++-v3/crossconfig.m4
+++ b/libstdc++-v3/crossconfig.m4
@@ -88,6 +88,13 @@ case "${host}" in
     AC_DEFINE(HAVE_HYPOT)
     ;;
 
+  *-fennix*)
+    GLIBCXX_CHECK_COMPILER_FEATURES
+    GLIBCXX_CHECK_LINKER_FEATURES
+    GLIBCXX_CHECK_MATH_SUPPORT
+    GLIBCXX_CHECK_STDLIB_SUPPORT
+    ;;
+
   *-freebsd*)
     SECTION_FLAGS='-ffunction-sections -fdata-sections'
     AC_SUBST(SECTION_FLAGS)