Italy's Francesco Bagnaia enjoyed a dream day as he retained his MotoGP world title and crowned it with victory in the final race of the season in Valencia on Sunday.

The 26-year-old Ducati rider had been assured of the championship when his sole rival Jorge Martin crashed early in the race.

Bagnaia had had his own nightmare crash when he suffered a leg injury in the Catalunya MotoGP in early September.

"It's a dream!" said Bagnaia of his title.

"I am super happy

"It's been a great season even if Barcelona and the leg injury made it really tough for the run-in.

"I've always dreamed of winning the title while also winning the race.

"I would like to pay tribute to the team, who have done an extraordinary job this season."

Bagnaia was leading at the time on his Ducati unaware that Martin had come to grief after his Ducati-Pramac clipped Marc Marquez's Honda resulting in both riders coming to grief.

Martin walked off shaking his hands in frustration whilst six-time champion Marquez limped away in what was his final race for Honda.

Martin returned to the pitlane where he burst into tears and was embraced by his team members after the crash that left the 93,000 spectators in shock.

"I did not see that Martin had crashed," said Bagnaia, even though his team held out a board to announce he was out.

"I thought he was still in the race and I was scared.

"I said to myself the best thing to do was to ride to win the race and that would ensure I retained the title."

Martin, 25, had made an excellent start, the Spaniard surging from sixth on the grid to second and pressuring Bagnaia.

However, on the second lap Martin clipped Bagnaia's bike and although he averted total disaster he dropped down to the eighth spot.

A few laps later, though, he was unable to save himself a second time and the title was delivered into 26-year-old Bagnaia's hands.

Bagnaia — who started from pole after Maverick Vinales was demoted for an infraction during the warm-up — rode a perfect race by contrast and regained the lead after Jack Miller crashed spectacularly.

Although last week's Qatar victor Fabio Di Giannantonio challenged him Bagnaia held his nerve and eased over the line, punching the air in delight as he recorded his seventh win of the campaign.

Di Giannantonio held off Frenchman Johann Zarco to take second.

"I am very happy," said Di Giannantonio.

"I was not feeling very good in the middle of the race.

"I found some reserves and thought I could pass him on the final lap but on the final corner I lost it and my head dropped."

Bagnaia after climbing off his bike proceeded to slam dunk a basketball and then put three gold rings onto his fingers.

It is the second successive year Bagnaia has won the title on the final day — Martin had reduced his lead to just 14 points on Saturday with victory in the sprint race.