Dowager Hatt is Sir Topham Hatt's elderly mother.
In her first visit to Sodor, Thomas was charged with bringing her to Kirk Ronan, where Gordon would then take her on a VIP tour. She later visited Sodor several times, including once to celebrate her birthday.
During her youth, she used to be a very good opera singer, though her son does not like hearing it. She owns a Dalmatian, which she renamed "Gremlin" after her adventure with Gordon's "gremlins".
She later attended Sir Robert Norramby's Christmas Luncheon and became cross when Sir Topham Hatt failed to show up for a lunch date, and went out to find him on board Thomas.
When her son caught a cold, Dowager Hatt forced him to stay home and ran the railway in his place. Confusion and delay quickly ensured, however, when she forced the engines to perform trivial tasks for her, such as sending Thomas to collect a new hat for her from the docks, and gave engines tasks unsuited to their abilities, such as having Percy pull the Express. When Emily pointed this out to her, she was saddened that she had failed her son. Fortunately, by working together, Dowager Hatt and Emily were able to get the railway back on track by the time Sir Topham returned that evening.
Dowager Hatt is a bit of a thrill-seeker, a big opera singer and hates going slow and resting. She loves her son, Sir Topham, and much like him, she does not stand any nonsense, and is shown to be stern with him when he does not do what she tells him to do just as he is stern with his engines, even though he is an adult.
Dowager Hatt usually wears a green dress and a green hat, with a gold band and a red flower on it. During the winter she wears a purple dress and purple hat with a lighter purple flower on it.
- Season 5 - Gordon and the Gremlin (not named)
- Season 6 - It's Only Snow (cameo) and Thomas the Jet Engine (cameo)
- Season 9 - Thomas and the Birthday Picnic (not named in US narration)
- Season 11 - Percy and the Left Luggage (not named in US narration)
- Season 12 - Excellent Emily (does not speak)
- Season 13 - Percy's Parcel
- Season 14 - Jitters and Japes
- Season 15 - Gordon and Ferdinand, Percy's New Friends (cameo), Edward the Hero, Up, Up and Away!, Stop That Bus!, Wonky Whistle (cameo), Tree Trouble and Fiery Flynn
- Season 16 - Express Coming Through, Percy and the Monster of Brendam (mentioned), Thomas and the Sounds of Sodor (cameo), Muddy Matters (cameo) and Happy Birthday Sir! (does not speak)
- Season 18 - Toad's Adventure, Samson Sent for Scrap (not named; mentioned) and Millie and the Volcano
- Season 19 - The Beast of Sodor, Diesel's Ghostly Christmas (cameo) and Reds vs. Blues (cameo)
- Season 20 - Engine of the Future and Buckled Tracks and Bumpy Trucks
- Season 21 - Dowager Hatt's Busy Day, A Shed for Edward (mentioned), Terence Breaks the Ice (cameo) and Confused Coaches
- 2008 - Percy and the Left Luggage (speaks in speech bubble only; mistaken for Lady Hatt)
- 2010 - Percy's Parcel (speaks in speech bubble only)
- 2011 - Jitters and Japes and Gordon and Ferdinand (does not speak)
- 2012 - Edward the Hero (cameo; mistaken for Lady Hatt), Where's That Bus?, Wonky Whistle (cameo), Express Coming Through! and Up, Up and Away! (does not speak)
- 2013 - Happy Birthday, Sir! (cameo) and The Fat Controller's Bedtime Story (Issue 662)
- 2014 - Whistle-Stop Tour (mentioned)
- Keith Wickham (UK/US; thirteenth season onwards)
- Fu Suzuki (Japan; fifth season only)
- Keiko Nemoto (Japan; ninth season onwards)
- Margrit Strassburger (Germany; thirteenth season onwards)
- Ewa Serwa (Poland; thirteenth - sixteenth seasons)
- Anna Apostolakis (Poland; eighteenth season onwards)
- Lena Meieran (Norway; thirteenth - sixteenth seasons, excluding Day of the Diesels)
- Marianne Westby (Norway; Day of the Diesels only)
- Talya Barkay (Israel; fifteenth season onwards)
- Blanche Ravalec (France and French speaking Canada; ninth season onwards)
- Loretta Santini (Latin America; thirteenth season onwards)
- Mercedes Espinosa (Spain)
- Susa Saukko (Finland; thirteenth season onwards)
- Her title, Dowager, means someone who is a widow with a noble title so this means that her husband is deceased.
- Dowager Hatt's appearance has changed over the course of the television series.
- Season 12:
- Her eye color changed from brown to blue.
- She appears to have lost a significant amount of weight.
- Season 18:
- The wrinkles on her forehead become more prominent.
- Her skin becomes paler.
- Season 12:
- "Well, Thomas. I must admit that, for once, my mother was right!"
- ―Sir Topham Hatt, Buckled Tracks and Bumpy Trucks, twentieth season