diff --git a/lib/spack/spack/cmd/env.py b/lib/spack/spack/cmd/env.py
index d75cf6b262..bf1f29d558 100644
--- a/lib/spack/spack/cmd/env.py
+++ b/lib/spack/spack/cmd/env.py
@@ -5,6 +5,7 @@
 
 import argparse
 import os
+import shlex
 import shutil
 import sys
 import tempfile
@@ -144,10 +145,13 @@ def create_temp_env_directory():
     return tempfile.mkdtemp(prefix="spack-")
 
 
-def env_activate(args):
-    if not args.activate_env and not args.dir and not args.temp:
-        tty.die("spack env activate requires an environment name, directory, or --temp")
+def _tty_info(msg):
+    """tty.info like function that prints the equivalent printf statement for eval."""
+    decorated = f'{colorize("@*b{==>}")} {msg}\n'
+    print(f"printf {shlex.quote(decorated)};")
 
+
+def env_activate(args):
     if not args.shell:
         spack.cmd.common.shell_init_instructions(
             "spack env activate", "    eval `spack env activate {sh_arg} [...]`"
@@ -160,12 +164,25 @@ def env_activate(args):
 
     env_name_or_dir = args.activate_env or args.dir
 
+    # When executing `spack env activate` without further arguments, activate
+    # the default environment. It's created when it doesn't exist yet.
+    if not env_name_or_dir and not args.temp:
+        short_name = "default"
+        if not ev.exists(short_name):
+            ev.create(short_name)
+            action = "Created and activated"
+        else:
+            action = "Activated"
+        env_path = ev.root(short_name)
+        _tty_info(f"{action} default environment in {env_path}")
+
     # Temporary environment
-    if args.temp:
+    elif args.temp:
         env = create_temp_env_directory()
         env_path = os.path.abspath(env)
         short_name = os.path.basename(env_path)
         ev.create_in_dir(env).write(regenerate=False)
+        _tty_info(f"Created and activated temporary environment in {env_path}")
 
     # Managed environment
     elif ev.exists(env_name_or_dir) and not args.dir:
diff --git a/lib/spack/spack/test/cmd/env.py b/lib/spack/spack/test/cmd/env.py
index 308e0b0e90..e291432a0f 100644
--- a/lib/spack/spack/test/cmd/env.py
+++ b/lib/spack/spack/test/cmd/env.py
@@ -2924,6 +2924,25 @@ def test_activate_temp(monkeypatch, tmpdir):
     assert ev.is_env_dir(str(tmpdir))
 
 
+def test_activate_default(monkeypatch):
+    """Tests whether `spack env activate` creates / activates the default
+    environment"""
+    assert not ev.exists("default")
+
+    # Activating it the first time should create it
+    env("activate", "--sh")
+    env("deactivate", "--sh")
+    assert ev.exists("default")
+
+    # Activating it while it already exists should work
+    env("activate", "--sh")
+    env("deactivate", "--sh")
+    assert ev.exists("default")
+
+    env("remove", "-y", "default")
+    assert not ev.exists("default")
+
+
 def test_env_view_fail_if_symlink_points_elsewhere(tmpdir, install_mockery, mock_fetch):
     view = str(tmpdir.join("view"))
     # Put a symlink to an actual directory in view
diff --git a/share/spack/qa/setup-env-test.fish b/share/spack/qa/setup-env-test.fish
index 6474917b70..589f4cbfa8 100755
--- a/share/spack/qa/setup-env-test.fish
+++ b/share/spack/qa/setup-env-test.fish
@@ -371,7 +371,6 @@ spt_contains " spack env list " spack env list --help
 
 title 'Testing `spack env activate`'
 spt_contains "No such environment:" spack env activate no_such_environment
-spt_contains "env activate requires an environment " spack env activate
 spt_contains "usage: spack env activate " spack env activate -h
 spt_contains "usage: spack env activate " spack env activate --help
 
@@ -415,6 +414,11 @@ spt_contains 'spack_test_2_env' 'fish' '-c' 'echo $PATH'
 spt_does_not_contain 'spack_test_env' 'fish' '-c' 'echo $PATH'
 despacktivate
 
+echo "Testing default environment"
+spack env activate
+contains "In environment default" spack env status
+despacktivate
+
 echo "Correct error exit codes for activate and deactivate"
 spt_fails spack env activate nonexisiting_environment
 spt_fails spack env deactivate
diff --git a/share/spack/qa/setup-env-test.sh b/share/spack/qa/setup-env-test.sh
index 4172a40155..b26619b9cd 100755
--- a/share/spack/qa/setup-env-test.sh
+++ b/share/spack/qa/setup-env-test.sh
@@ -140,7 +140,6 @@ contains " spack env list " spack env list --help
 
 title 'Testing `spack env activate`'
 contains "No such environment:" spack env activate no_such_environment
-contains "env activate requires an environment " spack env activate
 contains "usage: spack env activate " spack env activate -h
 contains "usage: spack env activate " spack env activate --help
 
@@ -197,6 +196,11 @@ contains "spack_test_2_env" sh -c 'echo $PATH'
 does_not_contain "spack_test_env" sh -c 'echo $PATH'
 despacktivate
 
+echo "Testing default environment"
+spack env activate
+contains "In environment default" spack env status
+despacktivate
+
 echo "Correct error exit codes for activate and deactivate"
 fails spack env activate nonexisiting_environment
 fails spack env deactivate
diff --git a/share/spack/setup-env.sh b/share/spack/setup-env.sh
index 91a601e652..a42882266c 100755
--- a/share/spack/setup-env.sh
+++ b/share/spack/setup-env.sh
@@ -126,8 +126,7 @@ _spack_shell_wrapper() {
                         # Space needed here to differentiate between `-h`
                         # argument and environments with "-h" in the name.
                         # Also see: https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html#Shell-Parameter-Expansion
-                        if [ -z ${1+x} ] || \
-                           [ "${_a#* --sh}" != "$_a" ] || \
+                        if [ "${_a#* --sh}" != "$_a" ] || \
                            [ "${_a#* --csh}" != "$_a" ] || \
                            [ "${_a#* -h}" != "$_a" ] || \
                            [ "${_a#* --help}" != "$_a" ];