Fleiss is a German surname meaning "diligence". Notable people with the surname include:
Heidi Fleiss (born 1965), American madam Jennifer Fleiss, American fashion executive Joseph L. Fleiss (1937–2003), American biostatistician Laura Kaeppeler-Fleiss (born 1988), American beauty pageant winner Mike Fleiss (born 1964), American television producer Nika Fleiss (born 1984), Croatian skier Noah Fleiss (born 1984), American actor Paul M. Fleiss (1933–2014), American pediatrician
See also Fleiss' kappa, a statistical measure of inter-rater reliability