Sale flanker White, the Scotland captain, beat Northampton's New Zealand fly-half Carlos Spencer into second place with Bristol scrum-half Shaun Perry third.
White's powerful performances have been instrumental in Sale finishing top of the Guinness Premiership - the Sharks are favourites to win the title at Twickenham on May 27 - and reaching the European Cup quarter-finals for the first time in the club's history.
The prestigious prize, won last year by England captain Martin Corry, is the pick of a notable awards hat-trick for White.
The 28-year-old was last month named Scotland's player of the year and he picked up the international player of the year award from the Scottish Professional Rugby Association.
White said: "When I was nominated initially I was surprised, and now to have won when the standard in the Guinness Premiership is so high, it is the greatest award I have ever had.
"I am over the moon and very honoured."
The other nominees for the PRA award were London Irish centre Mike Catt and Leeds' former All Black scrum-half Justin Marshall.
PRA young player of the year - the Nick Duncombe Memorial Award - went to Leicester and England winger Tom Varndell, the Premiership's leading try-scorer.
Varndell beat Newcastle's Commonwealth Games Sevens
hero Mathew Tait, Northampton centre Jon Clarke and loose-forwards Tom Rees of Wasps and Sale's Magnus Lund.
Varndell said: "It's a huge honour, especially with the other great young players nominated for the award.
"I've been fortunate enough to have a good season and I'm looking forward to the year ahead."
Tony Diprose, the retiring Harlequins and former England number eight, picked up the PRA Kingston Smith Special Merit Award for his outstanding contribution to rugby.
Matt Hampson, the Leicester and England Under-21 prop who severely injured his neck in a training ground accident, was awarded the THB Clowes Blyth Spirit Award for his remarkable courage.
Three legends of the game were inducted into the PRA Hall of Fame - English winger David Duckham, Irish centre Mike Gibson and Ian McGeechan, the former Scotland and Lions coach now in charge of Wasps.
The rugby highlight of the year was London Irish's extraordinary 56-37 victory over Wasps last month.
And London Irish winger Topsy Ojo won try of the year for his score against Bath in February.