Marcelina Klaudia Witek (born 2 June 1995) is a Polish track and field athlete who competes in the javelin throw. Her personal best is 66.53 m, set in 2018. She represented her country at the 2017 World Championships without qualifying for the final. In addition, she won a bronze medal at the 2017 European U23 Championships and a gold at the 2017 Summer Universiade.