Microsoft founder and philanthropist Bill Gates was pushed into second place by the Mexican telecom magnate, the second time Gates has lost top spot since 1995 in the Forbes magazine rankings.
Slim is worth a purported $53.5 billion while Gates has to make do with $53 billion, followed by US investor Warren Buffet on $47 billion.
The trio of well-heeled men have regained the combined $53.5 billion wiped off their fortunes in 2009.
The first Swede on the list is Ikea founder Ingvar Kamprad in 11th place. The Kamprad family fortune amounts to $23 billion. The richest Swedish resident is Stefan Persson of clothing chain H&M in 13th place with $22.4 billion.
Last year the Kamprads' then $22 billion fortune was enough to claim 5th place in the list. Persson has meanwhile expanded his wealth, from $14.5 billion last year, and climbed from 18th place as a result.
There are now 1,011 US dollar billionaires, in comparison to 793 in 2009 and 1,125 in 2008.
The net wealth of the world's billionaires has rebounded to $3.5 trillion, up $1.1 trillion on 2009 but still a way off 2008 levels of $4.4 trillion.
The number of women on the Forbes list of billionaires has increased from 72 in 2009 to 89.
"The global economy is recovering which can be seen reflected in the list this year," said the magazine's CEO Steve Forbes.