The 28-year-old has joined the Lions on a two-and-a-half-year contract until the end of the 2026-27 season, and Villa also possess the option to extend her stay for an extra 12 months.
Maritz, who is Villa Women's first signing of the January transfer window, leaves Arsenal after a three-and-a-half year spell in North London, having joined from Wolfsburg in the summer of 2020.
The California-born full-back came up with two goals in 92 appearances for the Gunners - netting both of those efforts in a 9-0 FA Cup annihilation of Crystal Palace in the 2020-21 season - but she struggled for starts in the run-up to Christmas.
Between November 5 and December 10, Maritz made the first XI in just one of Arsenal's five Women's Super League fixtures and was an unused substitute in a 1-0 North London derby defeat to Tottenham Hotspur on December 16.
Despite her recent lack of game time, Villa head coach Carla Ward hailed Maritz's arrival as a "really important" acquisition for Aston Villa, telling the club's website: "We're delighted to welcome Noelle to the club.
"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 won her first and only major honour with Arsenal Women in the 2022-23 League Cup, starting in the Gunners' 3-1 win over Chelsea in the final, prior to which she collected an FA Cup runners' up medal in 2021.
The defender - who began her senior career with FC Zurich - previously clinched one Champions League crown and five Bundesliga titles with Wolfsburg, and she has won 113 caps for the Swiss national team.
Maritz could make her debut for Aston Villa when Ward's side take on Everton in the fourth round of the Women's FA Cup next Saturday, after which the ninth-placed Lions resume WSL action away to Leicester City on January 21.