In a large soup pot, over medium heat, heat oil.
Add carrot, celery and onion.
Cook until vegetables have begun to soften and onion turn translucent, 3 to 4 minutes.
Stir in butternut squash, thyme, chicken broth, salt and pepper.
Bring to a boil, reduce heat and simmer until squash is fork-tender, about 30 minutes.
Use an immersion blender to purée soup.
Alternatively, let the soup cool slightly and carefully purée, in batches, in an upright blender.