diff --git a/20-which.sh b/20-which.sh
new file mode 100644
index 0000000..aa3b7eb
--- /dev/null
+++ b/20-which.sh
@@ -0,0 +1,48 @@
+#!/bin/bash
+
+if [ "`whoami`" == "root" ]; then
+  echo "Danger, Will Robinson!"
+  echo "Do not execute me as r00t"
+  exit 1
+fi
+
+TARBALL="which-2.21.tar.gz"
+DNL="https://ftp.gnu.org/gnu/which/which-2.21.tar.gz"
+SHA256="f4a245b94124b377d8b49646bf421f9155d36aa7614b6ebf83705d3ffc76eaad"
+
+[ -d which-2.21 ] && rm -rf which-2.21
+
+if [ ! -f ${TARBALL} ]; then
+  wget ${DNL}
+  if [ $? -ne 0 ]; then
+    echo "Could not retrieve ${DNL}"
+    echo "Sorry."
+    exit 1
+  fi
+fi
+
+CHECK="`sha256sum ${TARBALL} |awk ' { print $1 } ' `"
+if [ "${CHECK}" != "${SHA256}" ]; then
+  echo "${TARBALL} does not match expected SHA256. Sorry."
+  exit 1
+fi
+
+tar -zxf ${TARBALL} && cd which-2.21
+
+./configure --prefix=/usr
+if [ $? -ne 0 ]; then
+  echo "Configure script failed for which. Sorry."
+  exit 1
+fi
+
+make
+if [ $? -ne 0 ]; then
+  echo "Failed building which. Sorry."
+  exit 1
+fi
+
+echo "As the root user, run:"
+echo
+echo "  cd which-2.21"
+echo "  make install"
+echo
diff --git a/README.md b/README.md
index bcabf46..8fb82da 100644
--- a/README.md
+++ b/README.md
@@ -185,3 +185,14 @@ Requires CMake to build.
 * Script: [`19-brotli.sh`](19-brotli.sh)
 * Status: Script Untested
 * Note: Python bindings NOT built
+
+Dependency Twenty: which
+------------------------
+
+Justification: Needed for libseccomp test suite, and by *many* test suites and
+scripts on a GNU/Linux system. No build dependencies outside of LFS.
+
+* Script: [`20-which.sh`](20-which.sh)
+* Stutus: Script Untested
+
+