diff --git a/lldb/source/Commands/CommandCompletions.cpp b/lldb/source/Commands/CommandCompletions.cpp
--- a/lldb/source/Commands/CommandCompletions.cpp
+++ b/lldb/source/Commands/CommandCompletions.cpp
@@ -381,6 +381,8 @@
       Storage.append(RemainderDir);
     }
     SearchDir = Storage;
+  } else if (CompletionBuffer == path::root_directory(CompletionBuffer)) {
+    SearchDir = CompletionBuffer;
   } else {
     SearchDir = path::parent_path(CompletionBuffer);
   }
@@ -390,9 +392,11 @@
   PartialItem = path::filename(CompletionBuffer);
 
   // path::filename() will return "." when the passed path ends with a
-  // directory separator. We have to filter those out, but only when the
-  // "." doesn't come from the completion request itself.
-  if (PartialItem == "." && path::is_separator(CompletionBuffer.back()))
+  // directory separator or the separator when passed the disk root directory.
+  // We have to filter those out, but only when the "." doesn't come from the
+  // completion request itself.
+  if ((PartialItem == "." || PartialItem == path::get_separator()) &&
+      path::is_separator(CompletionBuffer.back()))
     PartialItem = llvm::StringRef();
 
   if (SearchDir.empty()) {
diff --git a/lldb/test/API/functionalities/completion/TestCompletion.py b/lldb/test/API/functionalities/completion/TestCompletion.py
--- a/lldb/test/API/functionalities/completion/TestCompletion.py
+++ b/lldb/test/API/functionalities/completion/TestCompletion.py
@@ -477,6 +477,19 @@
         self.complete_from_to("my_test_cmd main.cp", ["main.cpp"])
         self.expect("my_test_cmd main.cpp", substrs=["main.cpp"])
 
+    def test_completion_target_create_from_root_dir(self):
+        """Tests source file completion by completing ."""
+        root_dir = os.path.abspath(os.sep)
+        self.completions_contain(
+            "target create " + root_dir,
+            list(
+                filter(
+                    lambda x: os.path.exists(x),
+                    map(lambda x: root_dir + x + os.sep, os.listdir(root_dir)),
+                )
+            ),
+        )
+
     def test_target_modules_load_aout(self):
         """Tests modules completion by completing the target modules load argument."""
         self.build()