The Dane finished ahead of Nigel Melker (Tech 1 Racing) and Kevin Magnussen (DAMS), with the latter regaining the championship lead following the retirement of Stoffel Vandoorne (Fortec Motorsports).
"I hope this victory can be the turning point for our season," Sorensen said. "We really didn't have any luck at the start of the year. We need to finish the season in this vein, and work hard and do our best. I'm delighted with this win, which is my first since Spa last year."
Lotus driver Sorensen took his maiden FR 3.5 Series pole in the morning, qualifying ahead of fellow Dane Magnussen and Melker. The trio lined up on the grid ahead of Will Stevens (P1 by Strakka Racing) and Arthur Pic (AV Formula).
In an eventful start to the race, Melker slipped through into second to wedge himself between race leader Sorensen and third-placed Magnussen. A chaotic first lap saw Vandoorne fall back to 12th, while Pietro Fantin (Arden Caterham), Mikhail Aleshin (Tech 1 Racing) and Nikolay Martsenko (Pons Racing) all had to retire.
The safety car was introduced on lap 10 to allow Riccardo Agostini's car to be removed. The Zeta Corse man had spun and stopped on track during an attempt to overtake Matias Laine (P1 by Strakka Racing). The safety car was called into action again a short time later after contact between Norman Nato (DAMS) and Sergey Sirotkin (ISR). Vandoone, meanwhile, returned to the pits and subsequently retired from the race.
Unruffled by events around him, Sorensen eventually took victory ahead of Melker and Magnussen. Stevens finished fourth, followed by Pic and best-placed rookie William Buller (Zeta Corse).
Buller finished sixth after overtaking Antonio Félix da Costa (Arden Caterham), seventh, in the closing laps. Marlon Stockinger (Lotus) and André Negrão (International Draco Racing) followed, with Jazeman Jaafar (Carlin) also finishing in the points after fighting his way from the very back of the grid.
RED BULL RING - RACE ONE
1-Sorensen (DEN) - Lotus
2-Melker (NED) - Tech 1 Racing - +4.420
3-Magnussen (DEN) - DAMS - +9.065
4-Stevens (GBR) - P1 by Strakka Racing - +14.629
5-Pic (FRA) - AV Formula - +17.511
6-Buller (GBR) - Zeta Corse - +20.107
7-Da Costa (POR) - Arden Caterham - +21.411
8-Stockinger (PHI) - Lotus - +25.752
9-Negrao (BRA) - International Draco Racing - +27.699
10-Jaafar (MAL) - Carlin - +28.190