Mostert or Mostaert is a Dutch and Afrikaans metonymic occupational surname. Meaning "mustard", it originally referred to a mustard miller or salesman. The Middle Dutch spelling Mostaert and modern Dutch spelling Mosterd are among variant forms of the surname. People with these surnames include:Chaz Mostert, Australian racing driver Chris Mostert, Dutch saxophonist Franco Mostert, South African rugby player Frederick Mostert, South African trademark attorney and legal writer Gerhard Mostert, South African rugby player Heinz Mostert, German football defender Henk Mostert (1925–2002), Dutch correspondence chess player and president Herman Mostert, South African rugby player JP Mostert, South African rugby player Joseph Mostert (1912–1967), Belgian middle-distance runner Karla Mostert, South African netball player Mark Mostert, South African-born American non-fiction writer Mary Mostert (1929–2016), American Mormon missionary and writer Natasha Mostert, South African novelist and screenwriter Nicol Mostert, South African rugby player Phil Mostert (1898–1972), South African rugby player Raheem Mostert, American football running backMostaertAntoon Mostaert (1881–1971), Belgian Roman Catholic missionary in Inner Mongolia Frans Mostaert (1528–1598), Flemish landscape painter, twin brother of Gillis Gillis Mostaert (1528–1560), Flemish landscape painter, twin brother of Frans Jan Mostaert (c.1475–1553), Dutch portrait painter, possibly grandfather of Frans and Gillis