Caroline Ruhnau (born 16 October 1984) is a German swimmer. She competed at the 2012 Summer Olympics in the 100 m breaststroke, but failed to reach the final. She won this event at the European Short Course Swimming Championships 2009. She also won two bronze medals at European long-course championships in 2010 and 2012.
Her younger sister Alice is also a breaststroke swimmer. She swam on the next lane to Caroline at the Olympic trials in 2012.