The 28-year-old joins the Blues from Scottish Women’s Premier League champions Hearts after a brilliant season which saw her win the club’s Golden Boot award.
She bagged 19 goals and laid on six assists on the way to the title, also being named the club's Player of the Year and Players’ Player of the Year.
In total, Timms played more than 100 games for Hearts, scoring 45 goals and setting up 11 more.
She's also played for Oxford United and Lewes in her career to date.
Timms said: “I’m so happy to be here. The club, the direction it’s going in and speaking with the manager (David Wright) and speaking to Sean, it was the move that I wanted.”
Sean Burt, Town Women’s Technical Director, added: "We’re delighted Georgia has chosen to join us, she’s a player we identified quickly that we wanted to bring in this window after being a standout for a number of seasons in Scotland.
"Having worked with her previously and seen first hand her quality and personality, we’ve got no doubt she’ll be a fantastic addition."
Timms is the Tractor Girls' eighth signing of the summer so far. The others are:
Midfielder Jenna Slattery from Hearts
Midfielder Aimee Palmer from Southampton
Winger Rosie Livingstone from Hibernian
Winger Megan Hornby from Portsmouth
Forward Kit Graham from Spurs
Centre-back Georgia Hunter from Hearts
Forward Eilidh Adams from Hibernian