Kiwi driver Scott Dixon is a five-time IndyCar champion, after claiming a second-place finish in the season finale at Somoma, California.
Dixon only needed to better championship rival Alex Rossi to win the title.
The Kiwi benefited from Rossi's first-lap misfortune, when the American collided with teammate Michael Andretti, forcing an early stop for the challenger.
Dixon, starting second on the grid, followed winner Ryan Hunter-Reay the entire race, never dropping more than four seconds behind the American, and keeping the likes of Will Power and Joseef Newgarden at bay.
Dixon's fifth title leaves him behind only the great AJ Foyt on the all-time list, leapfrogging Mario Andretti in the process.
The 38-year-old avoided the first-lap carnage that saw Rossi drop to the back of the field, over a minute behind the lead.
Rossi managed to jump a few places after the first stop, but when Dixon lapped the American, it seemed the championship battle was over.
But a mistake from the Kiwi allowed Rossi to un-lap himself and when the yellow flag came out at the halfway point, he had a lifeline.
Graham Rahal stopped on the side of the track, causing the field to close up. Rossi found himself in 20th spot on fresh tyres and proceeded to power through the pack.
A little bit of carnage and a very quick car saw Rossi jump to fifth place with 21 laps still to run, just eight seconds back from the Kiwi who was running comfortably in second.
However the American's tyres started to falter in the dying stages and he eventually dropped to sixth, and with Dixon claiming second, the championship belonged to the Kiwi.
"This is so awesome," Dixon said.
"You always doubt these situations that it is going to happen.
"It is all about the people. I am the lucky one that gets to take it across the line.
"This doesn't come without a lot of hard work. We had a lot of things that could have gone wrong today.
"Rossi did a hell of a job. He pushed hard this year he is a real talent and has a big future ahead of him.
"We were just making sure we didn't get ourselves into an awkward moment that they could capitalize."
The Kiwi will be back to defend his title in 2019, having recently signed a two-year extension with Chip Ganassi Racing.
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