Mrs. Dowager Hatt is the Fat Controller and Sir Lowham Hatt's mother, Stephen and Bridget Hatt's great-grandmother, and Lady Hatt's mother-in-law. She owns a Dalmatian, which she renamed "Gremlin" after her adventure with Gordon's "gremlins". She is a bit of a thrill-seeker and hates going slow and resting.
During her youth, she used to be a very good opera singer. Though her son does not like hearing it.
- In the eighteenth season and onwards, Dowager Hatt has wrinkles and paler skin.
- In the twelfth season and onwards, her eye colour changed from brown to blue.
- Her name, Dowager, means someone who is a widow with a noble title. This possibly means that she is widow.
- Keith Wickham (UK/US; thirteenth season onwards)
- Fu Suzuki (Japan; fitth season only)
- Keiko Nemoto (Japan; ninth season onwards)
- Margrit Strassburger (Germany; thirteenth season onwards)
- Ewa Serwa (Poland)
- Lena Meieran (Norway; thirteenth - sixteenth season)
- Marianne Westby (Norway; Day of the Diesels onwards)
- Blanche Ravalec (France and French speaking Canada; ninth season onwards)
- Loretta Santini (Mexico; thirteenth season onwards)
- ERTL (discontinued)