diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 419c074a70..1030363238 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -182,6 +182,7 @@ jobs:
           - i686-unknown-linux-musl
           - powerpc64le-unknown-linux-gnu
           - riscv64gc-unknown-linux-gnu
+          - s390x-unknown-linux-gnu
           - x86_64-pc-windows-gnu
           - x86_64-pc-windows-msvc
           - x86_64-apple-darwin
@@ -255,6 +256,9 @@ jobs:
           - target: riscv64gc-unknown-linux-gnu
             host_os: ubuntu-22.04
 
+          - target: s390x-unknown-linux-gnu
+            host_os: ubuntu-22.04
+
           - target: x86_64-pc-windows-gnu
             host_os: windows-latest
 
@@ -342,6 +346,7 @@ jobs:
           - aarch64-unknown-linux-musl
           - i686-pc-windows-msvc
           - powerpc64le-unknown-linux-gnu
+          - s390x-unknown-linux-gnu
           - x86_64-unknown-linux-gnu
 
         mode:
@@ -363,6 +368,9 @@ jobs:
           - target: powerpc64le-unknown-linux-gnu
             host_os: ubuntu-22.04
 
+          - target: s390x-unknown-linux-gnu
+            host_os: ubuntu-22.04
+
           - target: x86_64-unknown-linux-gnu
             host_os: ubuntu-22.04
 
@@ -498,6 +506,7 @@ jobs:
           - i686-unknown-linux-gnu
           - powerpc64le-unknown-linux-gnu
           - riscv64gc-unknown-linux-gnu
+          - s390x-unknown-linux-gnu
           - x86_64-unknown-linux-musl
 
         mode:
@@ -527,6 +536,9 @@ jobs:
           - target: riscv64gc-unknown-linux-gnu
             host_os: ubuntu-22.04
 
+          - target: s390x-unknown-linux-gnu
+            host_os: ubuntu-22.04
+
           - target: x86_64-unknown-linux-musl
             host_os: ubuntu-22.04
 
diff --git a/include/ring-core/target.h b/include/ring-core/target.h
index 7ea6efabb8..3924e78f8d 100644
--- a/include/ring-core/target.h
+++ b/include/ring-core/target.h
@@ -46,6 +46,9 @@
 #elif defined(__riscv) && __SIZEOF_POINTER__ == 8
 #define OPENSSL_64_BIT
 #define OPENSSL_RISCV64
+#elif defined(__s390x__)
+#define OPENSSL_64_BIT
+#define OPENSSL_S390X
 #elif defined(__wasm__)
 #define OPENSSL_32_BIT
 #else
diff --git a/mk/cargo.sh b/mk/cargo.sh
index eae727a0a0..436b68eee2 100755
--- a/mk/cargo.sh
+++ b/mk/cargo.sh
@@ -23,6 +23,7 @@ qemu_arm="qemu-arm -L /usr/arm-linux-gnueabihf"
 qemu_mipsel="qemu-mipsel -L /usr/mipsel-linux-gnu"
 qemu_powerpc64le="qemu-ppc64le -L /usr/powerpc64le-linux-gnu"
 qemu_riscv64="qemu-riscv64 -L /usr/riscv64-linux-gnu"
+qemu_s390x="qemu-s390x -L /usr/s390x-linux-gnu"
 
 # Avoid putting the Android tools in `$PATH` because there are tools in this
 # directory like `clang` that would conflict with the same-named tools that may
@@ -114,6 +115,16 @@ case $target in
     export CARGO_TARGET_RISCV64GC_UNKNOWN_LINUX_GNU_LINKER=riscv64-linux-gnu-gcc
     export CARGO_TARGET_RISCV64GC_UNKNOWN_LINUX_GNU_RUNNER="$qemu_riscv64"
     ;;
+  s390x-unknown-linux-gnu)
+    export CC_s390x_unknown_linux_gnu=clang-$llvm_version
+    export AR_s390x_unknown_linux_gnu=llvm-ar-$llvm_version
+    # XXX: Using -march=zEC12 to work around a z13 instruction bug in
+    # QEMU 8.0.2 and earlier that causes `test_constant_time` to fail
+    # (https://lists.gnu.org/archive/html/qemu-devel/2023-05/msg06965.html).
+    export CFLAGS_s390x_unknown_linux_gnu="--sysroot=/usr/s390x-linux-gnu -march=zEC12"
+    export CARGO_TARGET_S390X_UNKNOWN_LINUX_GNU_LINKER=s390x-linux-gnu-gcc
+    export CARGO_TARGET_S390X_UNKNOWN_LINUX_GNU_RUNNER="$qemu_s390x"
+    ;;
   x86_64-unknown-linux-musl)
     export CC_x86_64_unknown_linux_musl=clang-$llvm_version
     export AR_x86_64_unknown_linux_musl=llvm-ar-$llvm_version
diff --git a/mk/install-build-tools.sh b/mk/install-build-tools.sh
index cb5b615f1c..b861041c1b 100755
--- a/mk/install-build-tools.sh
+++ b/mk/install-build-tools.sh
@@ -105,6 +105,14 @@ case $target in
     libc6-dev-riscv64-cross \
     qemu-user
   ;;
+--target=s390x-unknown-linux-gnu)
+  # Clang is needed for code coverage.
+  use_clang=1
+  install_packages \
+    qemu-user \
+    gcc-s390x-linux-gnu \
+    libc6-dev-s390x-cross
+  ;;
 --target=wasm32-unknown-unknown)
   cargo install wasm-bindgen-cli --bin wasm-bindgen-test-runner
   use_clang=1