The Chelsea owner, who topped all five previous lists published by the British magazine Fourfourtwo, is said to have lost more than $4.5 billion since the downturn in the world economy last year.
Chelsea's overall debt is believed to amount to almost $1 billion, the same amount as Manchester United. Chelsea's losses were the result of heavy expenditures by Abramovich on the transfer market. American Malcolm Glazer and his family borrowed heavily to buy United.
The other American on the top 10 list is Stanley Kroenke, who is invested heavily in American sports, including MLS (Colorado Rapids). He holds a minority interest in Arsenal.
Other new entries besides Sheikh and Kroenke are the Indian-born Lakshmi Mittal worth $18.8 billion, and Formula One's Bernie Ecclestone ($3.6 billion), who have invested in Championship (second division) Queen's Park Rangers.
FOOTBALL RICH LIST
1. Sheikh Mansour bin Zayed al Nahyan (Manchester City) $22.5 billion
2. Lakshmi Mittal and family (QPR) $18.8 billion
3. Roman Abramovich (Chelsea) $10.5 billion
4. Joe Lewis (Tottenham Hotspur) $3.75 billion
5. Bernie and Slavica Ecclestone (Queen's Park Rangers) $3.6 billion
6. Stanley Kroenke (Arsenal) $3.38 billion
7. Alisher Usmanov (Arsenal) $3 billion
8. Lord Grantchester and the Moores family (Everton) $1.8 billion
8. Dermot Desmond (Celtic) $1.8 billion
10. Lord Ashcroft (Watford) $1.65 billion
10. Malcolm Glazer and family (Manchester United) $1.65 billion