Coach Scott Frost made the announcement Sunday with the release of the team's Week 1 depth chart, selecting Martinez over redshirt freshman Tristan Gebbia. No true freshman has ever opened a season as the top QB for the Cornhuskers.
Nebraska opens the season Saturday at home against Akron.
The 6-foot-2, 220-pound Martinez was the prize signee in Frost's first recruiting class last December. He switched loyalty from Tennessee to Nebraska amid coaching upheaval at both schools, picking the Big Ten program after Frost flew cross-country to Fresno, California, to pursue Martinez even as the coach readied UCF for the Peach Bowl.
Martinez and Gebbia waged a race that heated up in March. Both Californians performed well in the spring game, though Martinez gained most of the attention for his four touchdowns and elusive running that appeared a strong fit in Frost's high-octane offense.
Ranked 103rd in the ESPN 300 for the Class of 2018, Martinez missed his senior season last fall at Clovis West High School in Fresno with a shoulder injury. He returned in January to play in the Under Armour All-America Game.
He will be called to lead an offense deep at running back and receiver amid heightened excitement at Nebraska around the return of Frost, the native son who led the Huskers as a QB to their most recent national championship in 1997.
Nebraska underperformed last year in winning just four games, its worst record since 1961.
The last Nebraska true freshman to start a game at QB was Cody Green in 2009. Tommie Frazier famously took over as the starter six games into the 1992 season as a true freshman -- ultimately helping push Frost, then a recruit, to pick Stanford over Nebraska. He transferred to Lincoln in 1995.