Per Fancred's Jon Heyman, Corbin's deal will be for six years and worth $140 million.
The Diamondbacks signed Corbin to a one-year, $7.5 million deal to avoid arbitration last January, and he was stellar with a chance to boost his stock in a contract year.
In 33 starts last season, the 29-year-old went 11-7 with a 3.15 ERA, 1.050 WHIP and 5.13 strikeout-to-walk rate en route to his second career All-Star nod.
Those numbers were aided by Corbin's quality fastball and one of MLB's hardest-to-hit sliders.
Additionally, he's excelled at keeping batters off balance thanks to the introduction of a slow curveball to his repertoire. According to FanGraphs, he threw the curve 9 percent of the time, and it clocked an average of 72.8 mph last year.
The Nationals will welcome Corbin and his refined three-pitch arsenal to one of a staff that already features three-time Cy Young Award winner Max Scherzer, Stephen Strasburg and Tanner Roark; Roark settled in and went 6-3 with a 3.43 ERA after the All-Star break last season.
Even with Bryce Harper potentially out of the picture as a free agent and the offense primed for a bit of regression, the pitching unit has a chance to keep the Nationals competitive at the top of the National League East alongside the Atlanta Braves and Philadelphia Phillies.