Monika Cassens (born February 28, 1953 in Tröbitz as Monika Thiere) is former a German badminton player.
She started her career in her birthplace, Tröbitz. For this club she won 15 national titles. After her marriage to Claus Cassens, she changed to SG Gittersee, a badminton club from Dresden. In her career she won 101 international tournaments. She won 6 Polish Open titles in a row in women's singles and women's doubles, and six titles in mixed doubles. 1990 she won the Malta International.