The stylish right-hander drove Corey Collymore to mid-on for four in his second innings in the third Test against the West Indies, taking him to 48 and past Richards' landmark of 1,710 runs, achieved in 1976.
The elated Yousuf raised his bat and looked to the skies with relief, then hit the next ball for another boundary and his half-century.
West Indies captain Brian Lara -- who had pledged that his side would try to stop Yousuf from beating his legendary predecessor's record -- applauded the Pakistani and went to congratulate him at the end of the over.
Yousuf achieved the feat in 11 Tests, the same number Richards' took to set the old record.
The Pakistani went on to reach his century in the afternoon session -- his second of the match and his ninth of 2006, breaking his own world record.
His fighting 102 in the first innings had already broken the record for hundreds in a 12-month calendar period, previously held by Richards (1976) and Sri Lanka's Aravinda de Silva (1997), with seven each.
The 32-year-old has previously attributed his prolific form both to his conversion from Christianity to Islam last year and also to the renewed team ethic in the Pakistani side.
Yousuf, who made his debut in South Africa in 1998, started the year with 461 runs in Pakistan's 1-0 win in the three-match home series against arch rivals India.
He missed one of the two Tests in Pakistan's away series against Sri Lanka and managed 31 runs in two innings there.
But the middle-order batsman stepped up a gear on the summer England tour, hitting a monumental 202 at Lord's. He scored a masterly 192 at Leeds and followed that up with 128 in the forfeited Oval Test.
His success continued in the current series against the West Indies, starting with a match-winning knock of 192 in the first Test in Lahore. His innings helped Pakistan clinch the match by nine wickets.
Yousuf then salvaged a draw for Pakistan in Multan with his 191, again missing a double century, and held the home team's innings again with his 102 in the first innings of this ongoing Test.
West Indian Richards, famous for his big hitting, achieved his record with a mammoth 829 runs in the four-match series against England in England in 1976. That total included 291 at The Oval and 232 at Nottingham.