Jack Grieves (born 5 December 2004) is an English professional footballer who plays as a forward for Watford.

Born in Watford, Grieves joined Watford for the second time in 2020, having already played for the club between the ages of eight and fourteen.^[1][2] He made his senior Watford debut on 7 January 2023, coming on as a second half substitute for Leandro Bacuna in a 2–0 home defeat to Reading in the second round of the FA Cup.

In June 2023, Watford announced that Grieves had been offered a professional contract with the club.^[3] The following month, he signed a three-year contract with the club holding an option to extend the deal by a further year.^[4]

Grieves hails from a footballing family, with a number of relatives playing for Watford. His great-grandfather was wing-half Reg Williams, while his great-great-grandfather was goalkeeper Skilly Williams.^[5] His father, Darren, most notably played for AFC Wimbledon, while his uncle, Danny, played as a midfielder.^[1][6]