Janszoon, sometimes abbreviated to Jansz, is a Dutch patronymic surname, meaning "son of Jan". People with this name or its variants include:
Aart Jansz Druyvesteyn (1577–1627), Dutch Golden Age painter
Anthonie Jansz. van der Croos (1606–1662), Dutch painter
Anthony Janszoon van Salee (1607–1676), original settler of and prominent, wealthy landholder, merchant, and creditor in New Netherland
Claes Jansz. Visscher, (1587–1652), Flemish draughtsman, engraver, printmaker and publisher
Diederik Jansz. Graeff, (1532–1589), first illustrious member of the De Graeff family, a rich merchant, Ship-owner and Politician
Dirk Jansz Smient, governor of Mauritius in the new settlement at Grand Port from 1666 to 1669, when he returned to Cape of Good Hope
Ernst Jansz (born 1948), one of the founding members and frontmen of Doe Maar
Frederica Jansz, Sri Lankan Burgher journalist, Editor of the Sunday Leader
Geoff Jansz (born 1958), Sri Lankan Australian Burgher chef and television presenter
Jacob Jansz. Coeman (born after 1676), Dutch painter of the 17th century
Jan Jansz. Weltevree (born 1595), Dutch sailor and probably the first Dutchman to visit Korea
Jan Jansz de Jonge Stampioen (1610–1690), Dutch mathematician famous for his published work on spherical trigonometry
Jan Janszoon, (1570–1641), first President and Grand Admiral of the Corsair Republic of Salè, Governor of Oualidia, and a Dutch pirate
Jan Janssonius, (1588–1664), also known as Jan Janszoon, Dutch cartographer
Jan Janszoon de Heem (1650–1695), Dutch Golden Age still-life painter
Job Janszoon van Meekeren (1611–1666), Dutch surgeon
Laurens Janszoon Coster (1370–1440), the inventor of the printing press from Haarlem
Lenaert Jansz de Graeff (1530–1578), son of Jan Pietersz Graeff, a rich cloth merchant from Amsterdam
Lucas Janszoon Waghenaer (1533–1606), Dutch chief officer and cartographer
Michiel Jansz. van Mierevelt, (1567–1641), Dutch Golden Age painter
Neville Jansz, Sri Lankan Burgher civil servant and diplomat
Pieter Jansz. Saenredam (1597–1665), painter of the Dutch Golden Age
Pieter Jansz van Asch (1603–1678), Dutch Golden Age painter
Salomon Jansz van den Tempel (1633–1673), 17th-century master shipbuilder
Willem Janszoon (1570–1630), Dutch navigator and colonial governor, is the first European known to have seen the coast of Australia
