"I accept this award on behalf of my teammates that have put me in a position to play well, coaches and of course my family.''
Williams helped the Sydney Roosters to the NRL premiership after returning to the code following five years in rugby union, during which he played 19 Tests for the All Blacks.
He has also been in devastating form at the World Cup and will hope to follow up the award with victory in Saturday's final against Australia at Old Trafford.
In taking out the gong, Williams broke an Australian stranglehold on the honour with Billy Slater (2008, 2011), Jarryd Hayne (2009), Todd Carney (2010) and Cameron Smith (2012) previous winners since it was established six years ago.
Williams was one three Kiwis named in the team of the year at a ceremony at The Lowry Hotel in Manchester, along with winger Roger Tuivasa-Sheck and hooker Issac Luke.
Inglis was named at fullback in the side, while Manly's Clive Churchill medallist Daly Cherry-Evans was named halfback of the year.
Sea Eagles centre Jamie Lyon and Brisbane veteran Corey Parker were the other Australians in the side.
South Sydney and England front rower George Burgess beat out Sydney Roosters backrower Boyd Cordner to be named rookie of the year while older brother Sam was best prop.
Super League player of the year Brough was the five-eighth of the year.
Trent Robinson was awarded coach of the year after guiding the Roosters to the NRL title in his first season in charge.
- AAP