Vernier has represented France at several Six Nations and played in every one of their games during the 2021 and 2025 World Cups.
She was ruled out of the Six Nations this spring midway through the tournament with a shoulder injury.
Vernier began her career with Racing Club Nanterre and also represented Lille MRCV, winning the title with the team in 2016.
“Her experience, physicality and game intelligence make her one of the standout centres in international rugby,” Gloucester-Hartpury head of rugby Dan Murphy said.
“Beyond her obvious qualities on the field, she’s a driven competitor whose standards and professionalism will have a hugely positive influence throughout our environment.”
