The 28-year-old is set to play the entire 2026 campaign, having featured 17 times for Southern Brave in The Hundred across 2021 and 2022, when she took 31 wickets.
Wellington said: "I'm really excited to join Hampshire for the upcoming season.
"I had a great time at Utilita Bowl in my two years at Southern Brave and I look forward to catching up with familiar faces and making new memories which will hopefully result in trophies come end the end of the summer."
Amanda-Jade Wellington will join Hampshire for the entirety of the 2026 season. (Image: Dave Vokes/Hampshire Cricket)
With 50 wickets, she is the second-highest wicket-taker in the history of the women's competition.
Her time in English cricket also includes a summer with Somerset, where in 2025 she was the side's leading wicket-taker in the One Day Cup with 19 wickets and contributed 282 runs.
In the Vitality Blast, she scored 254 runs at a strike rate of 130 and took 13 wickets, the second most for Somerset.
Adam Carty, regional director of women's cricket, said: "We're really pleased to secure Amanda-Jade for the whole of next season.
"She's a friend of the club and a vastly experienced cricketer, who boasts a fine record with bat and ball in England, having featured effectively in The Hundred and in Tier 1.
"We look forward to welcoming her back to Utilita Bowl in 2026."
Born in South Australia, Wellington was inspired by Shane Warne and taught herself how to bowl leg spin in her backyard.
She made her professional debut for South Australia at just 15, becoming the youngest player, male or female, to represent the state.
Her career highlights include 161 wickets for the Adelaide Strikers in the Women's Big Bash League, with best figures of 5-8 in the 2021-22 season.
On the international stage, Wellington has represented Australia 23 times, taking 30 wickets across all formats since her debut against South Africa in 2016.
Fans eager to follow the 2026 season can do so with a Hampshire Cricket membership, with adult packages starting at a discounted rate of £220 and junior memberships from £30.
The Early Bird discount is available until 11.59pm on Saturday, January 31.