Nikolia "Niki" Mitropoulou (; born February 16, 1982, in Galatsi, Athens) is a Greek high jumper. She attained her best jump of 1.91 metres from the Greek national championships to secure a spot on the Greek athletics squad for the 2004 Summer Olympics. Throughout her sporting career, Mitropoulou trained as a full-fledged member of the athletics team for Panionios G.S.S. in Nea Smyrni, Athens.
Mitropoulou qualified as a lone athlete for the Greek squad in the women's high jump at the 2004 Summer Olympics in Athens, by setting up a B-standard of 1.91 metres from the Greek national championships at the Olympic Stadium. Mitropoulou cleared a satisfying height on her third attempt and missed badly on the first two at both 1.80 and 1.85 metres to share a thirty-first overall place effort with Kazakhstan's Marina Aitova in the qualifying round, failing to reach a 1.89-metre mark on her succeeding jump and thereby advance further to the final.