Beckham and his wife Victoria’s collective wealth reached an estimated £1.185 billion (US$1.583 billion) this year, the Rich List compilers said.
That moved them into second place in the list of the UK’s wealthiest sportspeople, behind the family of ex-Formula One chief executive Bernie Ecclestone, whose wealth was valued at £2 billion.
Beckham, who retired from playing in 2013, is a co-owner of Inter Miami, estimated to be Major League Soccer’s most valuable club at £1.07 billion.
The 51-year-old also has lucrative brand ambassador roles for companies including Adidas and Hugo Boss.
Beckham captained England and won the Premier League and Champions League during a glittering career with United, before spells at Real Madrid, LA Galaxy, AC Milan and Paris Saint-Germain.
Victoria Beckham’s wealth has largely been generated from her fashion label after she originally found fame as a member of pop band The Spice Girls.
Joining Beckham on the Rich List, seven-time Formula One champion Lewis Hamilton is fifth on the list, having built a fortune the Rich List calculated at £435 million fortune.
Reigning Masters golf champion Rory McIlroy is seventh with an £325 million valuation.
Boxer Anthony Joshua is placed at eighth with a fortune of £240 million, one place above his heavyweight rival Tyson Fury, who is ninth on £162 million.
Bayern Munich and England striker Harry Kane and retired former Wimbledon champion Andy Murray are joint 10th with £110 million each.
Among business people with sporting associations, Manchester United co-owner Jim Ratcliffe has dropped down the overall Rich List.
His fortune shrank by £1.85 billion, according to the list compilers, to £15.194 billion.
The list compilers lowered the value of Ratcliffe’s petrochemicals company INEOS to £17 billion owing to “rising debt, falling revenues and a loss of £515.7 million”.
Promoters Barry and Eddie Hearn have joined Britain’s billionaire club, with their combined wealth estimated at £1.035 billion.
Barry is the founder and president of Matchroom Sport, one of the leading promoters in boxing, darts and snooker, while his son Eddie is chairman of the organisation.