The former England captain had firm offers from 12 different clubs but has opted for Ligue 1's big spenders.
Archive: Beckham's England highs and lows
Despite recently announcing he was to permanently base his family in London, Beckham always said he would make a decision on his next move based on "footballing reasons".
PSG have spent more than £200m in the last 18 months, and are managed by Carlo Ancelotti - who was in charge of AC Milan during Beckham's loan spell there. They are also still in this season's Champions League and will face Spanish side Valencia in the last 16.
The Paris club are currently top of Ligue 1 and already have a squad that includes Zlatan Ibrahimovic, Thiago Silva, Lucas Moura and Ezequiel Lavezzi.
Beckham, who made a record 115 outfield appearances for England, was part of the Manchester United side that famously beat Bayern Munich to win the 1999 Champions League.
He left Old Trafford for Real Madrid in 2003, before agreeing his move to LA Galaxy in January 2007 and making his debut for the club in August in that year.
He attracted criticism from some Galaxy fans after agreeing loan moves to AC Milan in 2009 and 2010 which meant missing some of the MLS season.
And he brought an end to his five-and-half-year spell in the United States on 2 December after winning the MLS Cup for the second time.
At PSG, Beckham will be hoping to win a league title in a fourth country, having already enjoyed success at Manchester United and Real Madrid in Europe before moving to Major League Soccer.
Beckham had been close to joining PSG last January but opted to stay in California for one more season.
PSG have been the highest-spending club in Europe in the past year and will officially present Beckham as their player at 16:00 GMT.
Beckham was undergoing a medical at Pitie-Salpetriere Hospital in Paris on Thursday afternoon.
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