Grabau is a surname. Notable people with the surname include:
Aaron Grabau (born 1978), Australian basketball player Amadeus William Grabau (1870–1946), geologist Charles Grabau, jurist Johannes Andreas August Grabau (1804–1879), theologian Lorenzo Grabau (born 1965), financier
See also Dorsum Grabau, geological feature on the moon Grabau, Lauenburg Grabau, Stormarn