Fleiss is a German surname meaning "diligence". Notable people with the surname include:
Elein Fleiss, French editor-in-chief of Purple Journal
Heidi Fleiss (born 1965), American former madam
Joseph L. Fleiss (1937–2003), American professor of biostatistics
Mike Fleiss (born 1964), American television producer
Nika Fleiss (born 1984), Croatian former skier
Noah Fleiss (born 1984), American actor
Paul M. Fleiss (1933–2014), American pediatrician