The Nevada State Athletic Commission confirmed McGregor's landmark purse to ESPN.com. McGregor will fight Diaz in a welterweight rematch in the main event of Saturday's UFC 202 card in T-Mobile Arena.
At UFC 196 in March, McGregor became the first UFC athlete to ever receive a disclosed purse of $1 million. Former heavyweight champion and WWE star Brock Lesnar surpassed that record at UFC 200 last month with a disclosed purse of $2.5 million.
McGregor will reclaim the distinction with this payday.
Diaz (19-10), who submitted McGregor in the second round of their first meeting, will make $2 million in disclosed pay.
Although the UFC does not disclose financial terms of its contracts, McGregor and Diaz are both likely to make much more in undisclosed pay-per-view bonuses.