diff --git a/.github/workflows/makefile.yml b/.github/workflows/makefile.yml
index 1b24768..d525d73 100644
--- a/.github/workflows/makefile.yml
+++ b/.github/workflows/makefile.yml
@@ -13,6 +13,7 @@ jobs:
     - uses: actions/checkout@v4
     - name: Install tools used in tests
       run: |
+        sudo apt install -y just
         npm install -g pnpm
     - name: Run tests
       run: dash run-tests.sh
diff --git a/README.md b/README.md
index d6824e2..84063b4 100644
--- a/README.md
+++ b/README.md
@@ -184,6 +184,7 @@ request.
 | Cabal        | Haskell          | `*.cabal`                                  | `cabal build` <br/> `cabal run` <br/> `cabal test`     |
 | Stack        | Haskell          | `stack.yaml`                               | `stack build` <br/> `stack run` <br/> `stack test`     |
 | make         | Any              | `Makefile`                                 | `make` <br/> `make test/check`                         |
+| just         | Any              | `justfile`                                 | `just build` <br /> `just run` <br /> `just test`      |
 | Mage         | Go               | `magefile.go` with a `test`/`check` target | `mage test/check`                                      |
 | Go           | Go               | `go.mod`                                   | `go test`                                              |
 | Tectonic     | LaTeX            | `Tectonic.toml`                            | `tectonic -X build`                                    |
diff --git a/man/projectdo.1 b/man/projectdo.1
index a7ed9a2..2719555 100644
--- a/man/projectdo.1
+++ b/man/projectdo.1
@@ -1,5 +1,5 @@
 '\" t
-.\" Automatically generated by Pandoc 3.1.13
+.\" Automatically generated by Pandoc 3.1.11.1
 .\"
 .TH "projectdo" "1" "April 24, 2024" "projectdo 0.2.2" "User Manual"
 .SH NAME
@@ -279,6 +279,21 @@ _
 tab(@);
 lw(8.4n) lw(10.9n) lw(23.5n) lw(27.2n).
 T{
+just
+T}@T{
+Any
+T}@T{
+\f[CR]justfile\f[R]
+T}@T{
+\f[CR]just build\f[R], \f[CR]just run\f[R], \f[CR]just test\f[R]
+T}
+_
+.TE
+.PP
+.TS
+tab(@);
+lw(8.4n) lw(10.9n) lw(23.5n) lw(27.2n).
+T{
 make
 T}@T{
 Any
diff --git a/man/projectdo.1.md b/man/projectdo.1.md
index cd51cd1..49487b5 100644
--- a/man/projectdo.1.md
+++ b/man/projectdo.1.md
@@ -124,6 +124,9 @@ alias p='projectdo tool'
 | Stack        | Haskell          | `stack.yaml`                          | `stack build`, `stack run`, `stack test`    |
 |--------------|------------------|---------------------------------------|---------------------------------------------|
 
+| just         | Any              | `justfile`                            | `just build`, `just run`, `just test`       |
+|--------------|------------------|---------------------------------------|---------------------------------------------|
+
 | make         | Any              | `Makefile`                            | `make`, `make test/check`                   |
 |--------------|------------------|---------------------------------------|---------------------------------------------|
 
diff --git a/projectdo b/projectdo
index c1a2645..e7b2135 100755
--- a/projectdo
+++ b/projectdo
@@ -187,6 +187,18 @@ try_lein() {
   fi
 }
 
+# justfile
+
+try_justfile() {
+  if [ -f justfile ]; then
+    if ! has_command "just"; then
+      echo "Found a justfile but 'just' is not installed."
+      exit 1
+    fi
+    execute_command just "$ACTION"
+  fi
+}
+
 # Makefile
 
 has_make_target() {
@@ -319,6 +331,7 @@ detect_and_run() {
   try_cmake
   try_maven
   try_lein
+  try_justfile
   try_makefile
   try_python
   try_go
diff --git a/run-tests.sh b/run-tests.sh
old mode 100644
new mode 100755
index d802cbd..83385be
--- a/run-tests.sh
+++ b/run-tests.sh
@@ -163,6 +163,25 @@ if describe "npm / yarn / pnpm"; then
   fi
 fi
 
+if describe "just"; then
+  if it "finds test target"; then
+    do_test_in "just"; assert
+    assertEqual "$RUN_RESULT" "just test"
+  fi
+  if it "finds build target"; then
+    do_build_in "just"; assert
+    assertEqual "$RUN_RESULT" "just build"
+  fi
+  if it "finds run target"; then
+    do_run_in "just"; assert
+    assertEqual "$RUN_RESULT" "just run"
+  fi
+  if it "can print tool"; then
+    do_print_tool_in "just"; assert
+    assertEqual "$RUN_RESULT" "just"
+  fi
+fi
+
 if describe "make"; then
   if it "finds check target"; then
     do_test_in "make-check"; assert
diff --git a/tests/just/justfile b/tests/just/justfile
new file mode 100644
index 0000000..e655633
--- /dev/null
+++ b/tests/just/justfile
@@ -0,0 +1,8 @@
+test:
+	@echo "Tests passed"
+
+build:
+	@echo "Built"
+
+run:
+	@echo "Ran"