Nathan Cleary says there is little more Penrith can do to prove they are the best team of the NRL era after his side claimed their fourth-straight premiership.

Panthers players celebrated their 14-6 grand final win over Melbourne long into Sunday night, the festivities at the Accor Stadium continuing until well after midnight.

Their fourth consecutive title made them the first team to achieve the feat in almost 60 years, when the great St George side won their last of their 11 straight in 1966.

South Sydney also won five straight between 1925 and 1929, as the only other team in the game's history to have claimed at least four titles on the trot.

Making Penrith's feat more remarkable is that, since the salary cap was introduced in 1990, only Brisbane (1992-23) and the Sydney Roosters (2018-19) have won back-to-back titles.

Asked how the title of being the best team of the NRL era sat with him, Cleary suggested that was now undisputed.

"In the NRL era, definitely. I don't think there's much more we can do," the Penrith halfback said.

"That Dragons team back then was an amazing term and achieved an amazing feat. But in terms of the NRL era, yeah, it's pretty crazy.

"We have lost great players along this journey, and we're going to lose more next year, but we just keep finding a way, people just step up.

"Paul Alamoti he's come in and losing Critta (Stephen Crichton) then Taylan May, and now he's up on the big stage just absolutely carving up.

"It's special to have that culture and just bring people in, and they just do their job and probably exceed it, to be honest."

Cleary's comments came as Andrew Johns declared in Nine's commentary that Penrith's achievements would likely never be repeated.

While the Panthers won late against South Sydney in 2021, dominated Parramatta in 2022 and pulled off a miracle comeback against the Broncos in 2023, they were forced to grind out Sunday night's win.

They dominated possession and territory, but were often engaged in long periods of arm wrestles throughout the match.

The game was also full of drama, with Melbourne star Cameron Munster forced to deny an alleged bite on Alamoti and Storm players upset over a no-try call in the second half.

Replays had initially suggested Jack Howarth had scored to make it 10-10, but the NRL were adamant after the game the bunker had been right to rule he was held up.

Still, a fifth title now looms as Penrith's greatest challenge, given the impending departures of two of their most crucial players in prop James Fisher-Harris and five-eighth Jarome Luai.

Asked what he would have thought had someone told him Penrith would win four on the bounce, Cleary smiled, "I would've said you're mad.

"There's definitely a belief there, but it's just exceeded all the dreams and expectations.

"But I think the beauty of it has just been staying present through the lot, just enjoying the journey that we're on, ticking off one after the other.

"It's just been an incredible ride, and one that we're still on - and we still want to keep achieving more things."