Top End teenager Keegan Payne catches million dollar fish on the ...

A diehard Top End fisher's late night barramundi haul has landed him a fortune — and a feed — as he becomes the first person to win the biggest prize in the Northern Territory's annual Million Dollar Fish competition.

Keegan Payne, a 19-year-old from the rural NT town of Katherine, snagged the lucrative $1 million barra bounty early on Sunday morning, while out fishing with mates and his sister on the Katherine River.

Keegan Payne, 19, reeled in the million dollar fish on the Katherine River.(ABC News: Matt Garrick)

"We weren't actually expecting a tagged barra at the time, until my little sister actually asked what it was in the fish," Mr Payne said.

"We were freakin' out.

"We nearly crashed the boat getting back to the boat ramp."

His 11-year-old sister, Addyson Payne, was onboard for the trip and was first to spot the coloured tag.

"We were sitting down and my brother's rod tipped," she said.

"He thought it was a catfish – but it was a barra.

"And they didn't see the tag, but I did, and I said; 'what's that sticking out of it?'

"And Keegan turned it around, and was like: 'No way, no way'.

"He was jumping around, screaming."

Keegan stands in a yard holding the fish in his hands, with Breanne at his side giving a thumbs up.(Supplied: Payne family)

The 67-centimetre barramundi has led to Mr Payne becoming Australia's newest millionaire, as he now deliberates on how to spread the money between himself and his seven siblings.

"The whole family was shocked – they're all proud of me," he said.

"We're from Katherine, Mum's from Kakadu.

"It's pretty hard going for us at the moment with money, but now with a million dollars, don't have to complain about it.

"It means a lot, we've got money, we can go places.

"We're actually planning a trip to America."

Mr Payne said he was heading out to buy a new boat, and possibly a car, this week.

Katherine teenager Keegan Payne arrived at the Darwin Waterfront by helicopter to receive his cheque.(ABC News: Matt Garrick)

The windfall follows a tough and tragic period for Mr Payne's family, after one of his brothers was killed in a caravan crash near Katherine in 2020.

The announcement comes on the last day of the annual fishing competition for 2024.

Earlier this year the NT government announced that it would guarantee a winner to the competition this season, but at the time didn't reveal exactly how that would happen.

The competition, which is paid out by sports gambling company SportsBet, was set up in a bid to lure tourists and fishers to the NT Top End in the quieter wet season months.

Katherine teenager Keegan Payne is the first ever winner of the Northern Territory's Million Dollar Fish competition.(ABC News: Matt Garrick)