The Welsh Premiership will be expanded to 14 teams for 2023-24 with no relegation in 2022-23.
Two teams will be promoted from the third tier Championship to expand the nation's second tier.
The Welsh Rugby Union's (WRU) decision came after a reduction to 10 teams was mooted.
WRU performance director Geraint John had already confirmed the Premiership season would conclude with play-offs for the top four.
The new campaign kicks off on Saturday, 3 September with reigning champions Cardiff going to Pontypridd for a 17:30 BST kick off.
The Premiership's last full season was 2018-19, with the two subsequent campaigns scrapped due to the Covid-19 pandemic before a reduced 11-game league season in 2021-22.
"Everybody's looking forward to hopefully an uninterrupted season," John added.
"These Premiership sides have had so many stop-starts, even last season when they didn't play the full home and away [fixtures].
"But this year they know they are playing home and away and know at the end there are play-offs and there's excitement around the place."
The new campaign starts in September and the forthcoming season will see Thursday evening games, which will be broadcast live on S4C.
"One of the reasons we went for Thursday nights was to try and attract younger people in," said Premiership chairman Jones, who is also chair of Ebbw Vale, one of the current 12 clubs.
"We kind of lost that younger audience over probably the last 20 years."
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