Lia Wälti, a 25-year-old midfielder, has made 54 appearances for Switzerland and spent five years with Turbine Potsdam.
She previously played in Switzerland for YB Frauen, where she won the Nationalliga A and played in the UEFA Champions League.
Gunners boss Joe Montemurro told www.arsenal.com: “Lia is a fantastic midfielder. She will give us another experienced option in that position. Her work-rate is impressive, and her professionalism will shine through.”
Meanwhile, the Gunners have arranged a pre-season friendly with Juventus at Boreham Wood FC for Sunday 5 August.