Robbert (Rop) Valentijn Gonggrijp is a Dutch hacker and one of the founders of XS4ALL.

XS4ALL was an Internet service provider (ISP) in the Netherlands. It was founded in 1993 as an offshoot of the hackers club Hack-Tic by Felipe Rodriquez, Rop Gonggrijp, Paul Jongsma and Cor Bosman, while based in Amsterdam. It was the sixth provider in the Netherlands and the second company to offer Internet access to private individuals. Initially only offering dial-in services via modem and ISDN, it later expanded to offer dial-up access as well as ADSL, VDSL, and fiber-optic (FTTH) services as well as mobile internet. The name is a play on the English pronunciation of access for all.