diff --git a/sys-cluster/openmpi/Manifest b/sys-cluster/openmpi/Manifest
index aad192529f006..687b6214d0a6d 100644
--- a/sys-cluster/openmpi/Manifest
+++ b/sys-cluster/openmpi/Manifest
@@ -1,3 +1,4 @@
 DIST openmpi-4.1.4.tar.bz2 10042839 BLAKE2B b020e3530ae5dde7b144e7c33b1a3f26f622526a4b48a97a0956fc6f49bbf9dfd5be9ebeeaf3bdc5168a307507408ba5dd8e2a537148821e1d476678177dc5d6 SHA512 c70a92c9b16b8c76a871183f9b180d60861186e64140da897d206d53bc06213f31ea93b31734645f580f4bf28dda5605d85dbce2417e4596955384d961bed653
 DIST openmpi-4.1.5.tar.bz2 10045426 BLAKE2B 135a8373ed6173b7a94def18e3b964c6b6050c909382e0dbb1898a6d261ae428931358121ef6d325d303f4f510017a94970f7c66b280a5fc460365821f36dece SHA512 7a2188684ed7542fe42e1717ae72cb859b4f3d6f722c9d3ba04bfed6c2178b3e7da3a536629d312c23571fed4d9b2ca5e20e85898ae5144e9332bd898e6e1cc6
 DIST openmpi-4.1.6.tar.bz2 10017002 BLAKE2B 4f119e1ed9b8787f0f860295ab1721fe2fd5300b8e182230a9eba3a864680b02bbd30618cc6d798a693a121626fc0ad5f447144d9ba91becb734f1a530d7a23a SHA512 0ef3240f9c436fb19b67e836cac376eafeb7825d12de3387dad04329dee9f182799d17d785ea23eba763810f479015bb5230593c28950b616b2f0aa1c0a81e71
+DIST openmpi-5.0.3.tar.bz2 29761888 BLAKE2B a084813f3dada12bbe77dcc6ef0ec0454980779f97ccb46f37f3d7df3bf7299e6484ec3427c2ca784e70876f62dc061a13cb7f08348e3d649e27f2bece9a09ac SHA512 60e8f6dcd6b1531ce8164e02f40be9a364ab484166a2a7b13bdff115a508f0596e97ad0a4204a47799ae608ba484a7ba9503042bddffe675f09ce22071b0b4a9
diff --git a/sys-cluster/openmpi/openmpi-5.0.3.ebuild b/sys-cluster/openmpi/openmpi-5.0.3.ebuild
new file mode 100644
index 0000000000000..f22be0582eaa7
--- /dev/null
+++ b/sys-cluster/openmpi/openmpi-5.0.3.ebuild
@@ -0,0 +1,141 @@
+# Copyright 1999-2024 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+FORTRAN_NEEDED=fortran
+inherit cuda flag-o-matic fortran-2 libtool
+
+MY_P=${P/-mpi}
+
+IUSE_OPENMPI_FABRICS="
+	openmpi_fabrics_ofed
+	openmpi_fabrics_knem"
+
+IUSE_OPENMPI_RM="
+	openmpi_rm_pbs
+	openmpi_rm_slurm"
+
+DESCRIPTION="A high-performance message passing library (MPI)"
+HOMEPAGE="https://www.open-mpi.org"
+SRC_URI="https://www.open-mpi.org/software/ompi/v$(ver_cut 1-2)/downloads/${MY_P}.tar.bz2"
+S="${WORKDIR}/${MY_P}"
+
+LICENSE="BSD"
+SLOT="0"
+KEYWORDS="~alpha ~amd64 -arm -ppc -x86 ~amd64-linux"
+IUSE="cma cuda cxx fortran ipv6 peruse romio valgrind
+	${IUSE_OPENMPI_FABRICS} ${IUSE_OPENMPI_RM}"
+
+REQUIRED_USE="
+	openmpi_rm_slurm? ( !openmpi_rm_pbs )
+	openmpi_rm_pbs? ( !openmpi_rm_slurm )
+"
+
+RDEPEND="
+	!sys-cluster/mpich
+	!sys-cluster/mpich2
+	!sys-cluster/nullmpi
+	>=dev-libs/libevent-2.0.22:=[threads(+)]
+	>=sys-apps/hwloc-2.0.2:=
+	sys-cluster/pmix:=
+	>=sys-libs/zlib-1.2.8-r1
+	cuda? ( >=dev-util/nvidia-cuda-toolkit-6.5.19-r1:= )
+	openmpi_fabrics_ofed? ( sys-cluster/rdma-core )
+	openmpi_fabrics_knem? ( sys-cluster/knem )
+	openmpi_rm_pbs? ( sys-cluster/torque )
+	openmpi_rm_slurm? ( sys-cluster/slurm )
+"
+DEPEND="${RDEPEND}
+	valgrind? ( dev-debug/valgrind )"
+
+pkg_setup() {
+	fortran-2_pkg_setup
+
+	elog
+	elog "OpenMPI has an overwhelming count of configuration options."
+	elog "Don't forget the EXTRA_ECONF environment variable can let you"
+	elog "specify configure options if you find them necessary."
+	elog
+}
+
+src_prepare() {
+	default
+	elibtoolize
+
+	# Avoid test which ends up looking at system mounts
+	echo "int main() { return 0; }" > test/util/opal_path_nfs.c || die
+
+	# Necessary for scalibility, see
+	# http://www.open-mpi.org/community/lists/users/2008/09/6514.php
+	echo 'oob_tcp_listen_mode = listen_thread' \
+		>> opal/etc/openmpi-mca-params.conf || die
+}
+
+src_configure() {
+	# -Werror=lto-type-mismatch, -Werror=strict-aliasing
+	# The former even prevents successfully running ./configure, but both appear
+	# at `make` time as well.
+	# https://bugs.gentoo.org/913040
+	# https://github.com/open-mpi/ompi/issues/12674
+	# https://github.com/open-mpi/ompi/issues/12675
+	append-flags -fno-strict-aliasing
+	filter-lto
+
+	local myconf=(
+		--disable-mpi-java
+		# configure takes a looooong time, but upstream currently force
+		# constriants on caching:
+		# https://github.com/open-mpi/ompi/blob/9eec56222a5c98d13790c9ee74877f1562ac27e8/config/opal_config_subdir.m4#L118
+		# so no --cache-dir for now.
+		--enable-mpi-fortran=$(usex fortran all no)
+		--enable-orterun-prefix-by-default
+		--enable-pretty-print-stacktrace
+
+		--sysconfdir="${EPREFIX}/etc/${PN}"
+
+		--with-hwloc=external
+		--with-libevent=external
+
+		# Oiriginally supposed to be re-enabled for 5.0!
+		# See https://github.com/open-mpi/ompi/issues/9697#issuecomment-1003746357
+		# and https://bugs.gentoo.org/828123#c14
+		#
+		# However as of 5.0.3 the docs still say:
+		#
+		#   As such, supporting data heterogeneity is a feature that has fallen
+		#   into disrepair and is currently known to be broken in this release
+		#   of Open MPI.
+		--disable-heterogeneous
+
+		$(use_enable cxx mpi-cxx)
+		$(use_enable ipv6)
+		$(use_enable peruse)
+		$(use_enable romio io-romio)
+
+		$(use_with cma)
+
+		$(use_with cuda cuda "${EPREFIX}"/opt/cuda)
+		$(use_with valgrind)
+		$(use_with openmpi_fabrics_knem knem "${EPREFIX}"/usr)
+		$(use_with openmpi_rm_pbs tm)
+		$(use_with openmpi_rm_slurm slurm)
+	)
+
+	CONFIG_SHELL="${BROOT}"/bin/bash econf "${myconf[@]}"
+}
+
+src_compile() {
+	emake V=1
+}
+
+src_test() {
+	emake -C test check
+}
+
+src_install() {
+	default
+
+	# Remove la files, no static libs are installed and we have pkg-config
+	find "${ED}" -name '*.la' -delete || die
+}