Mikołajczyk is a Polish surname derived from the name Mikołaj (Nicholas). Notable people with the surname include:
Erwin Mikolajczyk (died 1994), perpetrator of the 1994 Euskirchen court shooting Helena Mikołajczyk (born 1968), Polish biathlete Ron Mikolajczyk (born 1950), American football player Stanisław Mikołajczyk (1901–1966), prime minister of the Polish government-in-exile during World War II
See also Mikolajczak