diff --git a/ci/run_ctests.sh b/ci/run_ctests.sh
index fc1de8e1b4..3d77d3ae29 100755
--- a/ci/run_ctests.sh
+++ b/ci/run_ctests.sh
@@ -21,8 +21,14 @@ else
     exit 1
 fi
 
+# Skip ROUTING_* gtests when CUOPT_RUN_ROUTING_TESTS is false (e.g. PRs that don't touch routing)
+RUN_ROUTING_TESTS="${CUOPT_RUN_ROUTING_TESTS:-true}"
 for gt in "${GTEST_DIR}"/*_TEST; do
     test_name=$(basename "${gt}")
+    if [[ "${RUN_ROUTING_TESTS}" == "false" ]] && [[ "${test_name}" == ROUTING_* ]]; then
+        echo "Skipping gtest ${test_name} (routing tests not requested)"
+        continue
+    fi
     echo "Running gtest ${test_name}"
     "${gt}" "$@"
 done
diff --git a/ci/run_cuopt_pytests.sh b/ci/run_cuopt_pytests.sh
index 66e996715a..05d08aac46 100755
--- a/ci/run_cuopt_pytests.sh
+++ b/ci/run_cuopt_pytests.sh
@@ -9,4 +9,9 @@ set -euo pipefail
 # Support invoking run_cuopt_pytests.sh outside the script directory
 cd "$(dirname "$(realpath "${BASH_SOURCE[0]}")")"/../python/cuopt/cuopt/
 
-pytest -s --cache-clear "$@" tests
+# Skip routing tests when CUOPT_RUN_ROUTING_TESTS is false (e.g. PRs that don't touch routing)
+if [[ "${CUOPT_RUN_ROUTING_TESTS:-true}" == "false" ]]; then
+  pytest -s --cache-clear "$@" --ignore=tests/routing tests
+else
+  pytest -s --cache-clear "$@" tests
+fi
diff --git a/ci/test_cpp.sh b/ci/test_cpp.sh
index 653c44133a..c849ed0d4e 100755
--- a/ci/test_cpp.sh
+++ b/ci/test_cpp.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-# SPDX-FileCopyrightText: Copyright (c) 2023-2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-FileCopyrightText: Copyright (c) 2023-2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 # SPDX-License-Identifier: Apache-2.0
 
 set -euo pipefail
@@ -48,6 +48,13 @@ EXITCODE=0
 trap "EXITCODE=1" ERR
 set +e
 
+# Only in PR workflow: skip routing tests when PR doesn't touch routing code. Other runs (nightly, manual) run all tests.
+if [[ -z "${CUOPT_RUN_ROUTING_TESTS:-}" ]] && [[ "${GITHUB_REF:-}" == refs/heads/pull-request/* ]]; then
+  CI_DIR="$(cd "$(dirname "$(realpath "${BASH_SOURCE[0]}")")" && pwd)"
+  CUOPT_RUN_ROUTING_TESTS=$(bash "${CI_DIR}/utils/routing_changed.sh")
+  export CUOPT_RUN_ROUTING_TESTS
+fi
+
 # Run gtests from libcuopt-tests package
 export GTEST_OUTPUT=xml:${RAPIDS_TESTS_DIR}/
 
diff --git a/ci/test_python.sh b/ci/test_python.sh
index 0a70e56fa7..0e96de69fd 100755
--- a/ci/test_python.sh
+++ b/ci/test_python.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-# SPDX-FileCopyrightText: Copyright (c) 2023-2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-FileCopyrightText: Copyright (c) 2023-2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 # SPDX-License-Identifier: Apache-2.0
 
 set -euo pipefail
@@ -54,6 +54,13 @@ set +e
 # Due to race condition in certain cases UCX might not be able to cleanup properly, so we set the number of threads to 1
 export OMP_NUM_THREADS=1
 
+# Only in PR workflow: skip routing tests when PR doesn't touch routing code. Other runs (nightly, manual) run all tests.
+if [[ -z "${CUOPT_RUN_ROUTING_TESTS:-}" ]] && [[ "${GITHUB_REF:-}" == refs/heads/pull-request/* ]]; then
+  CI_DIR="$(cd "$(dirname "$(realpath "${BASH_SOURCE[0]}")")" && pwd)"
+  CUOPT_RUN_ROUTING_TESTS=$(bash "${CI_DIR}/utils/routing_changed.sh")
+  export CUOPT_RUN_ROUTING_TESTS
+fi
+
 rapids-logger "Test cuopt_cli"
 timeout 10m bash ./python/libcuopt/libcuopt/tests/test_cli.sh
 
diff --git a/ci/test_wheel_cuopt.sh b/ci/test_wheel_cuopt.sh
index d761b27214..839d698fa7 100755
--- a/ci/test_wheel_cuopt.sh
+++ b/ci/test_wheel_cuopt.sh
@@ -53,6 +53,13 @@ cd -
 RAPIDS_DATASET_ROOT_DIR="$(realpath datasets)"
 export RAPIDS_DATASET_ROOT_DIR
 
+# Only in PR workflow: skip routing tests when PR doesn't touch routing code. Other runs (nightly, manual) run all tests.
+if [[ -z "${CUOPT_RUN_ROUTING_TESTS:-}" ]] && [[ "${GITHUB_REF:-}" == refs/heads/pull-request/* ]]; then
+  CI_DIR="$(cd "$(dirname "$(realpath "${BASH_SOURCE[0]}")")" && pwd)"
+  CUOPT_RUN_ROUTING_TESTS=$(bash "${CI_DIR}/utils/routing_changed.sh")
+  export CUOPT_RUN_ROUTING_TESTS
+fi
+
 # Run CLI tests
 timeout 10m bash ./python/libcuopt/libcuopt/tests/test_cli.sh
 
diff --git a/ci/utils/routing_changed.sh b/ci/utils/routing_changed.sh
new file mode 100755
index 0000000000..2d9ddd92cf
--- /dev/null
+++ b/ci/utils/routing_changed.sh
@@ -0,0 +1,52 @@
+#!/bin/bash
+# SPDX-FileCopyrightText: Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Prints "true" if routing-related files changed vs origin/main, else "false".
+# Only used when running under the PR workflow (refs/heads/pull-request/*); other
+# workflows (nightly, manual test.yaml) run all tests and do not call this script.
+# Must be run from the repository root.
+
+set -euo pipefail
+
+ROUTING_PATTERNS=(
+    'python/cuopt/cuopt/routing/'
+    'python/cuopt/cuopt/tests/routing/'
+    'cpp/src/routing/'
+    'cpp/include/cuopt/routing/'
+    'cpp/tests/routing/'
+)
+
+# If explicitly set by caller, respect it
+if [[ -n "${CUOPT_RUN_ROUTING_TESTS:-}" ]]; then
+    if [[ "${CUOPT_RUN_ROUTING_TESTS}" == "false" ]]; then
+        echo "false"
+        exit 0
+    fi
+    echo "true"
+    exit 0
+fi
+
+# Not in a git repo or no merge base: run routing tests to be safe
+if ! git rev-parse --is-inside-work-tree &>/dev/null; then
+    echo "true"
+    exit 0
+fi
+
+MB=""
+if git fetch origin main --depth=500 2>/dev/null; then
+    MB=$(git merge-base HEAD origin/main 2>/dev/null) || true
+fi
+if [[ -z "${MB:-}" ]]; then
+    echo "true"
+    exit 0
+fi
+
+CHANGED=$(git diff --name-only "${MB}...HEAD" 2>/dev/null) || { echo "true"; exit 0; }
+for pat in "${ROUTING_PATTERNS[@]}"; do
+    if echo "${CHANGED}" | grep -qE "^${pat}"; then
+        echo "true"
+        exit 0
+    fi
+done
+echo "false"