diff --git a/dev-ml/llvm/Manifest b/dev-ml/llvm/Manifest
index 99a255186b5be..956f8fc3437d6 100644
--- a/dev-ml/llvm/Manifest
+++ b/dev-ml/llvm/Manifest
@@ -11,3 +11,4 @@ DIST llvm-project-19.1.7.src.tar.xz.sig 438 BLAKE2B 4015140f4ba77de45039bdbdfbaf
 DIST llvm-project-20.1.5.src.tar.xz 147239812 BLAKE2B 992ebec16a11f32f234ba8b9f228f27939cdaeaaba474a08da2564ba3075bb10ab92a44be704666bdd77f8294321d43da40bb9245c411a86cd53cff88223a91f SHA512 3b7e657714fa9b943c75ec9eeb903018ab4713b1c3370746ba68893220729f178dabb971515741519f24e7ad0fa1dbce1345572bcf1d1fc1e5de97e4d2900a6b
 DIST llvm-project-20.1.5.src.tar.xz.sig 566 BLAKE2B c8be202b475726817893e1fe5fe2d3ab02ea1d3130ccfdf4c2c29b46e6aef79091de78e8a9aef59416ac1120bb3af6fdf47464db9b27b8fb4cb4194b0444e571 SHA512 c1bd30af5f7bfa6cac73994e9068d2791d9d27e86375fb15ad426422ad00cb43ade226c1b91ecc7daa950efae62c86300e4290d59649310f4e8fab5bdcb264fe
 DIST llvm-project-7dc7c155251c0008d5d59b84f0c9056365740f11.tar.gz 235921149 BLAKE2B 2867e313cd25fee6975da9bf65365fa51ed8780f3f8fc95983fb6e8f5b2c38c6d7f75a386b0ec2d74bafad74472973f4e4e603a5a0754465ac2b75942b8e90c6 SHA512 f8bc383ff2a1af836357150efa5728c7df3cd862f56ffaf12b5fc56ef631f1048276ff00b89fcf4d224576fa1eda9811d971886aae0855a4d29178060eb89a49
+DIST llvm-project-f8ca9e59cb438bd35b29a6d7cf6d72f50673aec9.tar.gz 236069626 BLAKE2B 5547770a22e5fd0240c0e435d0b0af0ebd789aa72d6829250917f2df605f9a95c6756bc1afc9b611b176c1ba8394c757b94789511b98b38c6ade6cca4c9ce7f6 SHA512 b1fffd7d4f5ede9bcda759bc59cdd47373a44a3bbd31a50d1d213e438a59f1da3cc96780a1d17ecaeb14454822921476406a6c37493354169f72e1fab7b3a3be
diff --git a/dev-ml/llvm/llvm-21.0.0_pre20250528.ebuild b/dev-ml/llvm/llvm-21.0.0_pre20250528.ebuild
new file mode 100644
index 0000000000000..4763f0e9cb633
--- /dev/null
+++ b/dev-ml/llvm/llvm-21.0.0_pre20250528.ebuild
@@ -0,0 +1,107 @@
+# Copyright 1999-2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+PYTHON_COMPAT=( python3_{11..13} )
+inherit cmake llvm.org llvm-utils python-any-r1
+
+DESCRIPTION="OCaml bindings for LLVM"
+HOMEPAGE="https://llvm.org/"
+
+LICENSE="Apache-2.0-with-LLVM-exceptions UoI-NCSA"
+SLOT="0/${PV}"
+IUSE="+debug test"
+RESTRICT="!test? ( test )"
+
+RDEPEND="
+	>=dev-lang/ocaml-4.00.0:0=
+	dev-ml/ocaml-ctypes:=
+	~llvm-core/llvm-${PV}:=[debug?]
+	!llvm-core/llvm[ocaml(-)]
+"
+
+DEPEND="
+	${RDEPEND}
+"
+BDEPEND="
+	${PYTHON_DEPS}
+	dev-lang/perl
+	dev-ml/findlib
+"
+
+LLVM_COMPONENTS=( llvm cmake third-party )
+LLVM_USE_TARGETS=llvm
+llvm.org_set_globals
+
+src_configure() {
+	llvm_prepend_path "${LLVM_MAJOR}"
+
+	local libdir=$(get_libdir)
+	local mycmakeargs=(
+		-DLLVM_LIBDIR_SUFFIX=${libdir#lib}
+
+		-DBUILD_SHARED_LIBS=OFF
+		-DLLVM_BUILD_LLVM_DYLIB=ON
+		-DLLVM_LINK_LLVM_DYLIB=ON
+		-DLLVM_OCAML_OUT_OF_TREE=ON
+
+		# cheap hack: LLVM combines both anyway, and the only difference
+		# is that the former list is explicitly verified at cmake time
+		-DLLVM_TARGETS_TO_BUILD=""
+		-DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD="${LLVM_TARGETS// /;}"
+		-DLLVM_BUILD_TESTS=$(usex test)
+
+		# disable various irrelevant deps and settings
+		-DLLVM_ENABLE_FFI=OFF
+		-DLLVM_ENABLE_TERMINFO=OFF
+		-DHAVE_HISTEDIT_H=NO
+		-DLLVM_ENABLE_ASSERTIONS=$(usex debug)
+		-DLLVM_ENABLE_EH=ON
+		-DLLVM_ENABLE_RTTI=ON
+
+		-DLLVM_HOST_TRIPLE="${CHOST}"
+
+		-DPython3_EXECUTABLE="${PYTHON}"
+
+		# TODO: ocamldoc
+	)
+
+	use test && mycmakeargs+=(
+		-DLLVM_LIT_ARGS="$(get_lit_flags)"
+	)
+
+	# LLVM_ENABLE_ASSERTIONS=NO does not guarantee this for us, #614844
+	# also: custom rules for OCaml do not work for CPPFLAGS
+	use debug || local -x CFLAGS="${CFLAGS} -DNDEBUG"
+	cmake_src_configure
+
+	local llvm_libdir=$(llvm-config --libdir)
+	# an ugly hack; TODO: figure out a way to pass -L to ocaml...
+	cd "${BUILD_DIR}/${libdir}" || die
+	ln -s "${llvm_libdir}"/*.so . || die
+
+	if use test; then
+		local llvm_bindir=$(llvm-config --bindir)
+		# Force using system-installed tools.
+		sed -i -e "/llvm_tools_dir/s@\".*\"@\"${llvm_bindir}\"@" \
+			"${BUILD_DIR}"/test/lit.site.cfg.py || die
+	fi
+}
+
+src_compile() {
+	cmake_build ocaml_all
+}
+
+src_test() {
+	# respect TMPDIR!
+	local -x LIT_PRESERVES_TMP=1
+	cmake_build check-llvm-bindings-ocaml
+}
+
+src_install() {
+	DESTDIR="${D}" \
+	cmake -P "${BUILD_DIR}"/bindings/ocaml/cmake_install.cmake || die
+
+	dodoc bindings/ocaml/README.txt
+}