In what proved to be the only race at the Portuguese track to run its full 20-lap distance, Bautista extended his lead in the standings over Yamaha man Razgatlioglu to 56 points with only three rounds to go.
Kawasaki's Jonathan Rea could once again only manage third place and has now slipped 82 points behind Bautista.
It was Rea who led the opening phase of the race as he managed to grab the lead off poleman Razgatlioglu at the Turn 5 left-hander on the opening lap, with Bautista settling into third place behind his two nearest title rivals.
But Razgatlioglu stuck close to the rear wheel of Rea and was able to retake the lead into the first corner at the start of lap 7, holding off the Ulsterman the following lap as he tried to fight back at the same corner.
Next time by, Rea reasserted his authority as Bautista came close to making a double pass for the lead, slotting into second place behind the Ducati, before the Spaniard hit the front for the first time at the start of lap 10.
While Rea started to fade from the lead fight at this point, Razgatlioglu stuck with Bautista for several more laps, and after passing Rea for second he managed to briefly grab the lead back with a pass at the unusual location of Turn 13.
But just a few corners later Bautista used the superior straight-line speed of his works Ducati V4 R to retake the lead along the start/finish straight, and then eased away to 12th win of the season by a margin of 2.2 seconds.
Behind Rea, Michael Ruben Rinaldi was fourth aboard the second Ducati, holding off Alex Lowes aboard the Kawasaki by half a second.
Andrea Locatelli was a lonely sixth on his Yamaha ahead of top BMW rider Scott Redding and Honda man Xavi Vierge in eighth place, as Vierge's Honda teammate Lecuona crashed out at Turn 14 in the early stages.
Garrett Gerloff (GRT Yamaha) was best independent rider in ninth place following a rare crash for Motocorsa Ducati's Axel Bassani, while Loris Baz completed the top 10 aboard the Bonovo BMW.
Luca Bernardi was 13th on the Barni Ducati in his final race outing before being replaced by Xavi Fores for the final three races of the season.
MotoAmerica champion and Portimao wildcard Jake Gagne banked a single point for 15th place aboard his Attack Performance Yamaha.
Portimao WSBK - Race 3 results:
| Cla | # | Rider | Bike | Gap |
|---|---|---|---|---|
| 1 | 19 |
 Alvaro Bautista |
Ducati | |
| 2 | 1 |
 Toprak Razgatlioglu |
Yamaha | 2.256 |
| 3 | 65 |
 Jonathan Rea |
Kawasaki | 4.758 |
| 4 | 21 |
 Michael Ruben Rinaldi |
Ducati | 7.833 |
| 5 | 22 |
Alex Lowes |
Kawasaki | 8.406 |
| 6 | 55 |
Andrea Locatelli |
Yamaha | 15.191 |
| 7 | 45 |
Scott Redding |
BMW | 19.661 |
| 8 | 97 |
Xavi Vierge |
Honda | 20.581 |
| 9 | 31 |
 Garrett Gerloff |
Yamaha | 20.889 |
| 10 | 76 |
 Loris Baz |
BMW | 23.756 |
| 11 | 5 |
 Philipp Oettli |
Ducati | 24.047 |
| 12 | 60 |
 Michael van der Mark |
BMW | 25.749 |
| 13 | 29 |
 Luca Bernardi |
Ducati | 29.930 |
| 14 | 2 |
Roberto Tamburini |
Yamaha | 31.337 |
| 15 | 33 |
Jake Gagne |
Yamaha | 36.203 |
| 16 | 50 |
 Eugene Laverty |
BMW | 38.719 |
| 17 | 17 |
Marvin Fritz |
Yamaha | 41.026 |
| 18 | 23 |
Christophe Ponsson |
Yamaha | 48.489 |
| 19 | 35 |
 Hafizh Syahrin |
Honda | 48.591 |
| 20 | 36 |
 Leandro Mercado |
Honda | 48.727 |
| 21 | 3 |
 Kohta Nozane |
Yamaha | 49.505 |
| 22 | 7 |
Iker Lecuona |
Honda | 1'06.148 |
| 23 | 52 |
 Oliver Konig |
Kawasaki | 1'13.116 |
| 47 |
Axel Bassani |
Ducati | ||
| 91 |
Leon Haslam |
Kawasaki | ||
| 44 |
Lucas Mahias |
Kawasaki | ||
| View full results | ||||
