Niewiadomski (feminine: Niewiadomska) is a surname. Notable people with the surname include:
Eligiusz Niewiadomski (1869–1923), Polish painter and art critic Julia Niewiadomska (born 2002), Polish handballer Krzysztof Niewiadomski (born 1970), Polish luger Mariusz Niewiadomski (born 1959), Polish footballer Zbigniew Niewiadomski (born 1946), Polish sprint canoer