diff --git a/sci-mathematics/acl2/Manifest b/sci-mathematics/acl2/Manifest
new file mode 100644
index 0000000..2720dbe
--- /dev/null
+++ b/sci-mathematics/acl2/Manifest
@@ -0,0 +1 @@
+DIST acl2-8.4.tar.gz 202242463 BLAKE2B 887273910c7913d08455e5053a4c4d065743e0ba247f94f994a3400f27c97f8fce07debb145dbf26287c8b72e9335d995fcbc49f7085e17384b38035d260c8b8 SHA512 5a38271ffa9f9aad79d2aaf575144a58cf1b926b9ba3f9fb34af927862c95f6f683e870c9b453b2527abe8bdcd5603c6b5ad4c50b70c407606db78e0a79545bb
diff --git a/sci-mathematics/acl2/acl2-8.4.ebuild b/sci-mathematics/acl2/acl2-8.4.ebuild
new file mode 100644
index 0000000..f7a7bd7
--- /dev/null
+++ b/sci-mathematics/acl2/acl2-8.4.ebuild
@@ -0,0 +1,74 @@
+# Copyright 1999-2021 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+inherit elisp-common
+
+DESCRIPTION="Industrial strength theorem prover"
+HOMEPAGE="https://www.cs.utexas.edu/users/moore/acl2/"
+SRC_URI="https://github.com/acl2/acl2/archive/${PV}/${P}.tar.gz"
+
+LICENSE="BSD"
+SLOT="0/${PV}"
+KEYWORDS="~amd64 ~x86"
+IUSE="+books +doc emacs"
+
+RDEPEND=">=dev-lisp/sbcl-1.5.2:="
+DEPEND="${RDEPEND}"
+BDEPEND="emacs? ( >=app-editors/emacs-23.1:* )"
+
+PATCHES=( "${FILESDIR}"/${PN}-use_make_variable.patch )
+
+LISP="sbcl --noinform --noprint --no-sysinit --no-userinit --disable-debugger"
+SAVED_NAME=saved_acl2
+
+DOCS=( books/README.md )
+
+src_prepare() {
+	find . -type f -name "*.bak" -delete
+	find . -type f -name "*.orig" -delete
+
+	# Remove sparc binary inadvertently included in upstream
+	rm books/workshops/2003/schmaltz-al-sammane-et-al/support/acl2link || die
+
+	default
+}
+
+src_compile() {
+	emake LISP="${LISP}"
+
+	use books && emake ACL2="${S}"/${SAVED_NAME} basic
+	use doc && emake ACL2="${S}"/${SAVED_NAME} DOC
+
+	use emacs && elisp-compile emacs/*.el
+}
+
+src_install() {
+	sed -e "s|${S}|/usr/share/acl2|g" -i ${SAVED_NAME} || die
+	sed -e "5iexport ACL2_SYSTEM_BOOKS=/usr/share/acl2/books/"  \
+		-i ${SAVED_NAME} || die
+
+	dobin ${SAVED_NAME}
+	dosym ${SAVED_NAME} /usr/bin/${PN}
+
+	insinto /usr/share/acl2
+	doins ${SAVED_NAME}.core
+	use books && doins -r books
+
+	use doc && HTML_DOCS=( doc/HTML/. )
+	einstalldocs
+
+	if use emacs ; then
+		elisp-install ${PN} emacs/*{.el,elc}
+		doins TAGS
+	fi
+}
+
+pkg_postinst() {
+	use emacs && elisp-site-regen
+}
+
+pkg_postrm() {
+	use emacs && elisp-site-regen
+}
diff --git a/sci-mathematics/acl2/files/acl2-use_make_variable.patch b/sci-mathematics/acl2/files/acl2-use_make_variable.patch
new file mode 100644
index 0000000..32e0f05
--- /dev/null
+++ b/sci-mathematics/acl2/files/acl2-use_make_variable.patch
@@ -0,0 +1,13 @@
+use make variable to avoid QA issue: "make[1]: warning: jobserver unavailable: using -j1.  Add '+' to parent make rule"
+
+--- a/GNUmakefile
++++ b/GNUmakefile
+@@ -576,7 +576,7 @@ doc/home-page.html: doc/home-page.lisp
+ # xdoc::save that populates doc/manual/ (not under books/).
+ acl2-manual: check-books
+ 	rm -rf doc/manual books/system/doc/acl2-manual.cert
+-	cd books ; make USE_QUICKLISP=1 system/doc/acl2-manual.cert
++	cd books ; $(MAKE) USE_QUICKLISP=1 system/doc/acl2-manual.cert
+ 	rm -rf doc/manual/download/*
+ 
+ # WARNING: The dependency list just below isn't complete, since it
diff --git a/sci-mathematics/acl2/metadata.xml b/sci-mathematics/acl2/metadata.xml
new file mode 100644
index 0000000..86f685d
--- /dev/null
+++ b/sci-mathematics/acl2/metadata.xml
@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
+
+<pkgmetadata>
+  <longdescription>
+    ACL2 is both a programming language in which you can model computer systems
+    anda tool to help you prove properties of those models. ACL2 is part of
+    the Boyer-Moore family of provers, for which its authors have received the
+    2005 ACM Software System Award.
+  </longdescription>
+  <use>
+    <flag name="books">
+      build community books, the canonical collection of open-source libraries
+    </flag>
+  </use>
+  <upstream>
+    <bugs-to>https://github.com/acl2/acl2/issues/</bugs-to>
+    <remote-id type="github">acl2/acl2</remote-id>
+  </upstream>
+</pkgmetadata>