Ahead of the Misano weekend, Ducati confirmed Bastianini would join Bagnaia at the factory squad next year, with the pair reigniting their Le Mans duel in the latter stages of the San Marino GP.
Bagnaia prevailed in a tense run to the line to claim his fourth-successive victory and move to 30 points behind Yamaha’s Fabio Quartararo in the championship after the Frenchman could do no better than fifth.
Poleman Jack Miller grabbed the holeshot into Turn 1 ahead of Enea Bastianini and Bagnaia, who jumped up from fifth after a grid penalty knocked him from the second he qualified in.
Chaos ensued at the first corner behind as Pramac’s Johann Zarco, Ducati wildcard Michele Pirro and Honda’s Pol Espargaro were all taken out in a collision – with the latter walking away holding his wrist.
Miller’s charge would come to an end on lap two when he slid out of the lead at Turn 4, while Marco Bezzecchi on the VR46 Ducati crashed down at Turn 10.
Behind, Quartararo remained in eighth while Aleix Espargaro on the Aprilia jumped up to sixth on the opening lap.
The crashes for Miller and Bezzecchi promoted both one spot, but the top four of Bastianini – who took over the lead when Miller crashed – Bagnaia, Maverick Vinales on the sister Aprilia and VR46’s Luca Marini had broken away from the chasing pack.
Bastianini’s race almost went the same way as two of his Ducati counterparts when he lost the front-end into Turn 14 on the second lap.
The Gresini rider – sporting a tribute livery to the team’s late founder Fausto Gresini – stayed onboard and in the lead, though Bagnaia would come through at Turn 8 on the next tour.
Vinales quickly followed suit with aggressive lunge up the inside of Bastianini into Turn 14 to give chase on Bagnaia.
Behind, Quartararo capitalised on Espargaro running wide into Turn 13 on lap six to take fifth and started to marginally close the gap to the quartet ahead of him.
Bagnaia and Vinales would line astern for the next 16 laps, the Aprilia rider getting close at various points but never enough to execute a clean overtake on the Ducati.
Bastianini and Marini engaged in a brief battle for third on lap 16 throughs Turns 10 and the fast kink of Curvone at Turn 11, with the former holding firm.
This cast them both adrift slightly of the leading duo, but Bastianini rallied to reel in Vinales and move ahead into Turn 1 at the start of lap 20.
Bastianini proceeded to cut into Bagnaia’s lead and pressured him over the final tours, with the Gresini rider coming close to contact under braking for Turn 4.
This gave Bagnaia crucial metres with which to defend his lead, but Bastianini clawed that deficit back through the final sector.
Exiting the final corner nose to tail, Bagnaia got to the chequered flag just 0.034s ahead of Bastianini.
Vinales faded to third in the end, 4.2s off the victory, with Marini a solid fourth at his home race running a special VR46 livery.
Quartararo couldn’t bridge the gap to the podium and had to settle for a damage-limiting fifth, which only loses him two points from his championship lead.
Aleix Espargaro was a distant sixth in the end and tumbles to third in the standings, 33 behind Quartararo, with Alex Rins seventh on the Suzuki ahead of KTM’s Brad Binder, Pramac’s Jorge Martin and the LCR Honda of Alex Marquez.
Miguel Oliveira was 11th on his KTM after being forced to serve a long lap penalty for exceeding track limits too many times.
Andrea Dovizioso scored points in his final MotoGP race as he guided his RNF Yamaha home to 12th ahead of Tech3’s Raul Fernandez, Honda’s Stefan Bradl and LCR’s Takaaki Nakagami.
Darryn Binder missed out on points in 16th on the RNF Yamaha as Bezzecchi was 17th after re-joining from his crash. Miller shadowed him.
Remy Gardner was another forced to serve a long lap penalty on his Tech3 KTM which dropped him to 19th ahead of Gresini’s Fabio Di Giannantonio and Joan Mir’s Suzuki stand-in Kazuki Watanabe.
Yamaha’s Franco Morbidelli was involved in an incident with Di Giannantonio early on and ultimately retired from the race.
Full San Marino GP results:
| Cla | Rider | Bike | Gap | |
|---|---|---|---|---|
| 1 |  Jack Miller |
 |
Ducati | |
| 2 |  Francesco Bagnaia |
 |
Ducati | 0.015 |
| 3 | Enea Bastianini |
 |
Ducati | 0.115 |
| 4 | Marco Bezzecchi |
 |
Ducati | 0.149 |
| 5 |  Maverick Viñales |
 |
Aprilia | 0.219 |
| 6 |  Johann Zarco |
 |
Ducati | 0.270 |
| 7 | Luca Marini |
 |
Ducati | 0.327 |
| 8 | Fabio Quartararo |
 |
Yamaha | 0.347 |
| 9 | Aleix Espargaro |
 |
Aprilia | 0.678 |
| 10 |  Miguel Oliveira |
 |
KTM | 0.876 |
| 11 | Franco Morbidelli |
 |
Yamaha | 1.452 |
| 12 | Alex Rins |
 |
Suzuki | 1.539 |
| 13 | Jorge Martin |
 |
Ducati | 0.116 |
| 14 | Fabio Di Giannantonio |
|
Ducati | 0.377 |
| 15 |  Brad Binder |
 |
KTM | 0.701 |
| 16 | Alex Marquez |
 |
Honda | 0.732 |
| 17 | Michele Pirro |
 |
Ducati | 0.759 |
| 18 | Andrea Dovizioso |
 |
Yamaha | 0.764 |
| 19 | Pol Espargaro |
 |
Honda | 0.927 |
| 20 |  Stefan Bradl |
|
Honda | 0.939 |
| 21 | Darryn Binder |
 |
Yamaha | 1.432 |
| 22 |  Takaaki Nakagami |
 |
Honda | 1.585 |
| 23 | Kazuki Watanabe |
 |
Suzuki | 4.390 |
| 24 | Remy Gardner |
 |
KTM | 12.791 |
| 25 | Raúl Fernández |
 |
KTM | 14.833 |
| View full results | ||||
