The 19-year-old completed her paperwork with the club before linking up with the England squad ahead of the Women’s Under-19s European Championship this summer.
Zoe Johnson, managing director of women’s and girls’ football, said: “Hannah is an exciting young talent and we’re delighted to welcome her to the club on her first professional contract.
“We’re confident in her ability to perform in a highly demanding environment, which has already earned her a well-deserved place with the England team this summer.
“We’re excited to start working with her when she returns from the Euros, and we wish her luck in the tournament.”
Poulter was a product of the Reading academy, working her way up through the ranks to feature on the bench for the senior team aged just 16.
She was a regular among the under-21 squad and won the County Cup with the Royals in 2022.