diff --git a/dev-debug/valgrind/Manifest b/dev-debug/valgrind/Manifest
index ce6e48dc72b77..00aa2c15ca4d7 100644
--- a/dev-debug/valgrind/Manifest
+++ b/dev-debug/valgrind/Manifest
@@ -1,3 +1,5 @@
 DIST valgrind-3.26.0-patches-1.tar.xz 8092 BLAKE2B e2e4874ddd9129128153fc2ad0a35e6ecf4f81662c416257624600750c80cf959ff41ab5de06d47a841d640d9dfa0bb965f067d8c08d815931c6dd02c5fcd0bf SHA512 d55f283b834d3be572b4b2cdbdc11a15975162333052bbf77b3b7a0c29b170d332427d4ce24b2790aacabe737f02ef6ad4f2898ca625378631513fb60aaaba58
 DIST valgrind-3.26.0.tar.bz2 17182495 BLAKE2B 55e066b49e122f65df0c7129f25613f2d64fef6b4a7da59f42280e1a5a4086db84d033b8fca714b7ec8da506dbc71e8814f68f5b3d302c7373dbce8dac905b03 SHA512 80ebf9197be602fdd4aad0e9277e6ef2fd25ede9cecb6e6d159f6f062c13f62ad907c6b6e7000e82b3404d8b4f9e7bf15813f60d9fed414c7b713a4280c82898
 DIST valgrind-3.26.0.tar.bz2.asc 228 BLAKE2B 7ee59c96f5929e2de3478c062208e5fcf645e86f0894cb9b6330bb320b518f2e55e432ab31c813c623208216859ddcfcb673417c5a2be3982f2a9d23f4dcd698 SHA512 ecae4158c64bc4ff9c6c5859f41d8a724c5207b5dbac75772d64c23baf78a280159b1b954a16ac73993eb19c39e1fcb3bd0c946c0e18209f3cb8f3d9238d6071
+DIST valgrind-3.27.0.RC1.tar.bz2 17251319 BLAKE2B be6fa63788639b512776a57bf55b8410a3e69ca9bbc621f291ca89271cae88bbd61c2cd6efcd84463c6fad5d28737c06c8232fd665791268e0ccfa40c19efefb SHA512 f7b4b7976b4455baf91fcee27398402fceb9171e366758e45ccddfb25ee4b2ee56bfc8cf9f3c18550ec7929c5ed6f14f41df530911bb87d6941d29d682017ded
+DIST valgrind-3.27.0.RC1.tar.bz2.asc 228 BLAKE2B 033ce7f0f97df87442cabc056a4ed235bfef1030e4a87aef081b1ab9e2c8e5d19bfb4169cc1d972fd5966a3cf62bc3721137be45209b898520452602d1d81bc0 SHA512 64e8ad6ba24e27416be36eb853af945db5700ee820ff897b0fd9c4abb9eee04643177798c989083223cfffa878d0a177ed35cbcfaa8c23e745442e7ff6ce1fd8
diff --git a/dev-debug/valgrind/valgrind-3.27.0_rc1.ebuild b/dev-debug/valgrind/valgrind-3.27.0_rc1.ebuild
new file mode 100644
index 0000000000000..d9ec373663006
--- /dev/null
+++ b/dev-debug/valgrind/valgrind-3.27.0_rc1.ebuild
@@ -0,0 +1,203 @@
+# Copyright 1999-2026 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+# The Valgrind upstream maintainer also maintains it in Fedora and will
+# backport fixes there which haven't yet made it into a release. Keep an eye
+# on it for fixes we should cherry-pick too:
+# https://src.fedoraproject.org/rpms/valgrind/tree/rawhide
+#
+# Also check the ${PV}_STABLE branch upstream for backports.
+
+inherit autotools dot-a flag-o-matic toolchain-funcs multilib pax-utils
+
+DESCRIPTION="An open-source memory debugger for GNU/Linux"
+HOMEPAGE="https://valgrind.org"
+
+if [[ ${PV} == 9999 ]]; then
+	EGIT_REPO_URI="
+		https://sourceware.org/git/${PN}.git
+		https://git.sr.ht/~sourceware/valgrind
+	"
+	inherit git-r3
+else
+	VERIFY_SIG_OPENPGP_KEY_PATH=/usr/share/openpgp-keys/valgrind.asc
+	inherit verify-sig
+
+	MY_P="${P/_rc/.RC}"
+	MY_P="${MY_P%%_p*}"
+	VALGRIND_PATCH_TARBALL="${MY_P}-patches-${PV##*_p}"
+	SRC_URI="
+		https://sourceware.org/pub/valgrind/${MY_P}.tar.bz2
+		verify-sig? ( https://sourceware.org/pub/valgrind/${MY_P}.tar.bz2.asc )
+	"
+	# Rollups of backports on ${PV}_STABLE branch upstream. This branch
+	# is usually announced on the mailing list and distros are encouraged
+	# to pull from it regularly.
+	if [[ ${PV} == *_p* ]] ; then
+		SRC_URI+=" https://dev.gentoo.org/~sam/distfiles/${CATEGORY}/${PN}/${VALGRIND_PATCH_TARBALL}.tar.xz"
+	fi
+
+	S="${WORKDIR}"/${MY_P}
+
+	if [[ ${PV} != *_rc* ]] ; then
+		KEYWORDS="-* ~amd64 ~arm ~arm64 ~ppc ~ppc64 ~riscv ~x86 ~x64-macos ~x64-solaris"
+	fi
+fi
+
+LICENSE="GPL-3+"
+SLOT="0"
+IUSE="mpi"
+
+DEPEND="mpi? ( virtual/mpi )"
+RDEPEND="${DEPEND}"
+if [[ ${PV} == 9999 ]] ; then
+	# Needed for man pages
+	BDEPEND+="
+		app-text/docbook-xsl-stylesheets
+		dev-libs/libxslt
+	"
+else
+	BDEPEND+=" verify-sig? ( >=sec-keys/openpgp-keys-valgrind-20251018 )"
+fi
+
+PATCHES=(
+	# Respect CFLAGS, LDFLAGS
+	"${FILESDIR}"/${PN}-3.7.0-respect-flags.patch
+	"${FILESDIR}"/${PN}-3.15.0-Build-ldst_multiple-test-with-fno-pie.patch
+	"${FILESDIR}"/${PN}-3.21.0-glibc-2.34-suppressions.patch
+)
+
+QA_CONFIG_IMPL_DECL_SKIP+=(
+	# "checking if gcc accepts nested functions" but clang cannot handle good
+	# errors and reports both "function definition is not allowed here" and
+	# -Wimplicit-function-declaration. bug #900396
+	foo
+	# FreeBSD function, bug #932822
+	aio_readv
+)
+
+src_unpack() {
+	if [[ ${PV} == 9999 ]] ; then
+		git-r3_src_unpack
+	elif use verify-sig ; then
+		# Needed for downloaded patch (which is unsigned, which is fine)
+		verify-sig_verify_detached "${DISTDIR}"/${MY_P}.tar.bz2{,.asc}
+	fi
+
+	default
+}
+
+src_prepare() {
+	# Correct hard coded doc location
+	sed -i -e "s:doc/valgrind:doc/${PF}:" docs/Makefile.am || die
+
+	# Don't force multiarch stuff on OSX, bug #306467
+	sed -i -e 's:-arch \(i386\|x86_64\)::g' Makefile.all.am || die
+
+	if [[ ${CHOST} == *-solaris* ]] ; then
+		# upstream doesn't support this, but we don't build with
+		# Sun/Oracle ld, we have a GNU toolchain, so get some things
+		# working the Linux/GNU way
+		find "${S}" -name "Makefile.am" -o -name "Makefile.tool.am" | xargs \
+			sed -i -e 's:-M,/usr/lib/ld/map.noexstk:-z,noexecstack:' || die
+		cp "${S}"/coregrind/link_tool_exe_{linux,solaris}.in
+	fi
+
+	if [[ ${PV} != 9999 && -d "${WORKDIR}"/${VALGRIND_PATCH_TARBALL} ]] ; then
+		PATCHES+=( "${WORKDIR}"/${VALGRIND_PATCH_TARBALL} )
+	fi
+
+	default
+
+	eautoreconf
+}
+
+src_configure() {
+	local myconf=(
+		--with-gdbscripts-dir="${EPREFIX}"/usr/share/gdb/auto-load
+	)
+
+	tc-is-lto && myconf+=( --enable-lto )
+	lto-guarantee-fat
+
+	# Respect ar, bug #468114
+	tc-export AR
+
+	# -fomit-frame-pointer	"Assembler messages: Error: junk `8' after expression"
+	#                       while compiling insn_sse.c in none/tests/x86
+	# -fstack-protector     more undefined references to __guard and __stack_smash_handler
+	#                       because valgrind doesn't link to glibc (bug #114347)
+	# -fstack-protector-all    Fails same way as -fstack-protector/-fstack-protector-strong.
+	#                          Note: -fstack-protector-explicit is a no-op for Valgrind, no need to strip it
+	# -fstack-protector-strong See -fstack-protector (bug #620402)
+	# -m64 -mx32			for multilib-portage, bug #398825
+	# -fharden-control-flow-redundancy: breaks runtime ('jump to the invalid address stated on the next line')
+	filter-flags -fomit-frame-pointer
+	filter-flags -fstack-protector
+	filter-flags -fstack-protector-all
+	filter-flags -fstack-protector-strong
+	filter-flags -m64 -mx32
+	filter-flags -fsanitize -fsanitize=*
+	filter-flags -fharden-control-flow-redundancy
+	append-cflags $(test-flags-CC -fno-harden-control-flow-redundancy)
+	filter-lto
+
+	if use amd64 || use ppc64; then
+		! has_multilib_profile && myconf+=("--enable-only64bit")
+	fi
+
+	# Force bitness on darwin, bug #306467
+	use x64-macos && myconf+=("--enable-only64bit")
+
+	# Don't use mpicc unless the user asked for it (bug #258832)
+	if ! use mpi; then
+		myconf+=("--without-mpicc")
+	fi
+
+	econf "${myconf[@]}"
+}
+
+src_test() {
+	# fxsave.o, tronical.o have textrels
+	# -fno-strict-aliasing: https://bugs.kde.org/show_bug.cgi?id=486093
+	emake CFLAGS="${CFLAGS} -fno-strict-aliasing" LDFLAGS="${LDFLAGS} -Wl,-z,notext" check
+}
+
+src_install() {
+	if [[ ${PV} == 9999 ]]; then
+		# TODO: Could do HTML docs too with 'all-docs'
+		emake -C docs man-pages FAQ.txt
+		mv docs/FAQ.txt . || die "Couldn't move FAQ.txt"
+	fi
+
+	default
+
+	dodoc FAQ.txt
+
+	pax-mark m "${ED}"/usr/$(get_libdir)/valgrind/*-*-linux
+
+	strip-lto-bytecode
+
+	# See README_PACKAGERS
+	dostrip -x /usr/libexec/valgrind/vgpreload* /usr/$(get_libdir)/valgrind/*
+
+	if [[ ${CHOST} == *-darwin* ]] ; then
+		# fix install_names on shared libraries, can't turn them into bundles,
+		# as dyld won't load them any more then, bug #306467
+		local l
+		for l in "${ED}"/usr/lib/valgrind/*.so ; do
+			install_name_tool -id "${EPREFIX}"/usr/lib/valgrind/${l##*/} "${l}"
+		done
+	fi
+}
+
+pkg_postinst() {
+	elog "Valgrind will not work if libc (e.g. glibc) does not have debug symbols."
+	elog "To fix this you can add splitdebug to FEATURES in make.conf"
+	elog "and remerge glibc. See:"
+	elog "https://bugs.gentoo.org/214065"
+	elog "https://bugs.gentoo.org/274771"
+	elog "https://bugs.gentoo.org/388703"
+}