Maritz, 28, has signed a two-and-a-half year deal with the option of a further year, subject to approval from the Football Association.
She has 113 international caps and scored twice in 92 Arsenal appearances after joining from VfL Wolfsburg in 2020.
"We're delighted to welcome Noelle to the club," said Villa manager Carla Ward.
"She comes with a wealth of experience at the highest level having played in the Champions League as well as winning trophies wherever she's been.
"It's a really important signing for us as we continue to develop. She will add quality and experience to an evolving backline and we're delighted she's chosen to continue her journey with us."
Maritz had only made eight appearances for Arsenal this season.
Arsenal are currently third in the WSL table, behind Chelsea and Manchester City, while Villa are ninth.
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