- "Well, thank you, my dear. I knew this was my special birthday party, but I didn't know it was fancy dress!"
- ―Lady Hatt greeting her husband, Lady Hatt's Birthday Party, fifth season
Lady Jane Hatt (née Brown) is Sir Topham Hatt's wife and the sister of Sir Handel Brown I. She is also the mother of Sir Charles Topham Hatt II, the grandmother of Stephen and Bridget Hatt, the aunt of Sir Handel Lloyd Brown II, and the sister-in-law of Sir Lowham Hatt.
Lady Hatt occasionally helps her husband with railway business, and the engines sometimes go to extreme lengths to help throw parties for her birthday. She likes the railway, but had a certain dislike for Annie and Clarabel until they were cleaned and repainted. Although her husband runs a railway, she likes a day out on a boat or in their car.
Percy had the job of taking Lady Hatt to Great Waterton for a surprise; to see the brass band.
The engines are extremely fond of her and like when she visits the railway or rides in one of their coaches. A kind and gentle woman, Lady Hatt usually praises the engines for their good deeds.
In the first season, Lady Hatt's original outfit consisted of a white top with a light blue blouse with matching jeans. Her hair was also short.
In the third season, Lady Hatt was portrayed in a brief cameo wearing a blue button down. However, the rest of her attire is not shown. Her figure also slimmed and remains the appearance from the third season onwards.
In the fifth season, as well as a portrait image cameo in Thomas and the Magic Railroad, her attire consisted of a pink shirt with an indigo sweater with a white pearl necklace. However, in Lady's Hatt's Birthday Party, she was seen wearing a pink evening gown in the ending sequence.
From the seventh season onward, Lady Hatt's current outfit consists of a blue dress combined with a white trim sweater with a pink heart picture, with matching shoes, and matching hat with a pink hatband and matching flower.
In The Green Controller and in a cameo in Topped Off Thomas, Lady Hatt's appearance temporarily changed; her outfit she had on was a light blue two button dress with a beige hat with a black hatband. She has ever since returned to her seventh season onward outfit.
- Teresa Gallagher (UK; thirteenth season onwards - US; seventeenth season only)
- Jules de Jongh (US; thirteenth season onwards - excluding seventeenth season)
- Fu Suzuki (Japan; fifth and seventh seasons)
- Ikumi Sugiyama (Japan; tenth - thirteenth seasons)
- Sakura Yoshioka (Japan; Day of the Diesels onwards)
- Ewa Serwa (Poland; thirteenth season onwards)
- Benedikte Kruse (Norway; thirteenth - fifteenth seasons, excluding Day of the Diesels)
- Marianne Westby (Norway; Day of the Diesels only)
- Gabriela Guzmán (Latin America; thirteenth season onwards)
- Sabine Hahn (Germany; Audio Books only)
- Margrit Strassburger (Germany; thirteenth season onwards)
- Blanche Ravalec (France and French speaking Canada; tenth season onwards)
- María Sánchez (Spain)
- Susa Saukko (Finland; thirteenth season onwards)
- Olga Kuznetsova (Russia)
- Elain Llwyd (Wales)
- According to Lady Hatt's Birthday Party, Lady Hatt's birthday is during the summer.
- Lady Hatt is the only human character to have a namecard.
- In the Magazines, Lady Hatt is commonly referred to as "Lady Topham Hatt". This was what Wooden Railway called her as well. She is occasionally mistaken for Dowager Hatt also.
- Lady Hatt has changed a few times through the series:
- In the third season, Lady Hatt's appearance drastically changed.
- In the seventh season, she had less makeup on.
- From the twelfth season and onwards, she gained red lipstick.
- Her eye colour has also changed several times, they were blue in season one, black in seasons three through nine, blue again in The Green Controller, black again from the rest of season ten until The Great Discovery, and brown from season twelve and onwards.