Near-complete results show he easily removed the standard of 1,144 associates to secure the nomination.
Mr Glove romney said he was "humbled". He is the first Mormon from a major celebration to competition the presidential selection.
He is set to be formally anointed as the Republican nominee at the celebration meeting in California in overdue Aug.
Mr Glove romney has been the presumptive nominee for several weeks as his competitors withdrew or revoked campaigning.
With 1,086 associates properly secured as he joined the Arizona competition, Mr Glove romney only needed 58 to pass the 1,144 level. Arizona prizes 152 associates proportionally.
In near-complete profits, Mr Glove romney taken 63% of the election, according to the Associated Press, more than 10 times as many as his nearest competing, Ron Bob.
He will exceed his father, Henry Glove romney, a former Mich governor who ran ineffectively for the Republican nomination in 1968.
Opinion forms recommend Glove Mitt romney is kept in an extremely close competition with Mr Obama in Nov.
Birther row
"I am abided by that People in america across the country have given their assistance to my candidacy and I am humbled to have won enough associates to become the Republican Person's 2012 presidential nominee," Mr Glove romney said in declaration.
As forms shut, the former Boston governor was joining a fundraising in Las Nevada with property magnate Brian Trump.
He invested the day campaigning in Co and The state of las vegas.
Ahead of Tuesday's private fundraising, the Obama promotion launched a movie concentrating on Mr Trump's feedback wrongly claiming that the chief executive was blessed in South africa.
The movie looks for to sketch a comparison between Mr Glove romney and Senator Bob McCain, the 2008 Republican nominee, who once repaired a woman after she called Mr Obama a Islamic.
"Why won't Glove Mitt romney do the same?" demands the preview.
On Wednesday, Mr Glove romney ceased short of condemning Mr Trump's feedback.
"I don't acknowledge with all the people who assistance me. And my think is they don't all acknowledge with everything I believe in," Mr Glove romney told correspondents.
The Obama promotion movie against Mr Trump is the latest in a sequence of assault ads.
On Wednesday, the Glove romney promotion launched an assault ad criticising Mr Obama over a federal loan to a screen manufacturer which later went broke.
On Thursday Mr Glove romney also met on line internet gambling house magnate Sheldon Adelson, who provided large numbers to followers of Newt Gingrich's promotion during the primary season.
Experts say the result of November's selection could rely on what happens in a few arena declares, such as Co and The state of las vegas, as the applicants vie for the assistance of separate voters.
The next question of the promotion is who Mr Glove romney will pick as his vice-presidential running friend.
