diff --git a/masque/ports.py b/masque/ports.py
index ac48681..ff3a0e3 100644
--- a/masque/ports.py
+++ b/masque/ports.py
@@ -328,6 +328,9 @@ class PortList(metaclass=ABCMeta):
             duplicates = (set(self.ports.keys()) - set(mapping.keys())) & set(mapping.values())
             if duplicates:
                 raise PortError(f'Unrenamed ports would be overwritten: {duplicates}')
+        missing = set(mapping) - set(self.ports)
+        if missing:
+            raise PortError(f'Ports to rename were not found: {missing}')
 
         for kk, vv in mapping.items():
             if vv is None or vv != kk:
@@ -395,6 +398,14 @@ class PortList(metaclass=ABCMeta):
         Raises:
             `PortError` if the ports are not properly aligned.
         """
+        if not connections:
+            raise PortError('Must provide at least one port connection')
+        missing_a = set(connections) - set(self.ports)
+        if missing_a:
+            raise PortError(f'Connection source ports were not found: {missing_a}')
+        missing_b = set(connections.values()) - set(self.ports)
+        if missing_b:
+            raise PortError(f'Connection destination ports were not found: {missing_b}')
         a_names, b_names = list(zip(*connections.items(), strict=True))
         a_ports = [self.ports[pp] for pp in a_names]
         b_ports = [self.ports[pp] for pp in b_names]
diff --git a/masque/test/test_ports.py b/masque/test/test_ports.py
index 070bf8e..14dc982 100644
--- a/masque/test/test_ports.py
+++ b/masque/test/test_ports.py
@@ -70,6 +70,25 @@ def test_port_list_rename() -> None:
     assert "B" in pl.ports
 
 
+def test_port_list_rename_missing_port_raises() -> None:
+    class MyPorts(PortList):
+        def __init__(self) -> None:
+            self._ports = {"A": Port((0, 0), 0)}
+
+        @property
+        def ports(self) -> dict[str, Port]:
+            return self._ports
+
+        @ports.setter
+        def ports(self, val: dict[str, Port]) -> None:
+            self._ports = val
+
+    pl = MyPorts()
+    with pytest.raises(PortError, match="Ports to rename were not found"):
+        pl.rename_ports({"missing": "B"})
+    assert set(pl.ports) == {"A"}
+
+
 def test_port_list_plugged() -> None:
     class MyPorts(PortList):
         def __init__(self) -> None:
@@ -88,6 +107,25 @@ def test_port_list_plugged() -> None:
     assert not pl.ports  # Both should be removed
 
 
+def test_port_list_plugged_empty_raises() -> None:
+    class MyPorts(PortList):
+        def __init__(self) -> None:
+            self._ports = {"A": Port((10, 10), 0), "B": Port((10, 10), pi)}
+
+        @property
+        def ports(self) -> dict[str, Port]:
+            return self._ports
+
+        @ports.setter
+        def ports(self, val: dict[str, Port]) -> None:
+            self._ports = val
+
+    pl = MyPorts()
+    with pytest.raises(PortError, match="Must provide at least one port connection"):
+        pl.plugged({})
+    assert set(pl.ports) == {"A", "B"}
+
+
 def test_port_list_plugged_mismatch() -> None:
     class MyPorts(PortList):
         def __init__(self) -> None: