The structure for this season's competition has been changed to a home and away format, with no play-offs at the end of the campaign. The top 11 of the 16 teams will retain their Premiership status for next season.
The club finished 12th will face off against the winners of the WRU National Championship, which was the 'invincibles' of Pontypool last season after they completed an unbeaten campaign, to determine the final place in next season's 12-team league.
The play-off game will only take place if the Championships winners have the required criteria that meets the requirements for clubs to play in the following 12-team Premiership in 2019/20.
WRU head of performance, Geraint John, said the changes to the structure were in collaboration with the clubs.
"We felt it was a common sense approach as it gives all teams 15 homes fixtures and 15 away games. We listened to the clubs feedback and with no ring fencing in this year's competition, it should lead to an exciting season ahead," he said.
Last season's winners Merthyr take on Cardiff at the Arms Park, runners-up Llandovery, head to Bargoed to kick-off their campaign, while third placed Pontypridd are also on the road in Round 1, facing a tricky trip to Bedwas.
Newport will travel to Carmarthen Quins, before hosting Bargoed, whilst Ebbw Vale head Llanelli in round 1 then the Wizards at Eugene Cross.
Principality Premiership Fixtures 2018/19 (First Month Only)
Round 1: 1 September
Aberavon v Swansea
Bargoed v Llandovery
Bedwas v Pontypridd
Cardiff v Merthyr
Carmarthen Quins v Newport
Cross Keys v Bridgend
Llanelli v Ebbw Vale
RGC 1404 v Neath
Round 2: 8 September
Carmarthen Quins v Cross Keys
Ebbw Vale v Aberavon
Llandovery v Cardiff
Merthyr v Bedwas
Neath v Bridgend
Newport v Bargoed
Pontypridd v Llanelli
Swansea v RGC 1404
Round 3: 15 September
Aberavon v Pontypridd
Bargoed v Carmarthen Quins
Bedwas v Llandovery
Bridgend v Swansea
Cardiff v Newport
Cross Keys v Neath
Llanelli v Merthyr
RGC 1404 v Ebbw Vale
Round 4: 22 September
Bargoed v Cross Keys
Carmarthen Quins v Cardiff
Ebbw Vale v Bridgend
Llandovery v Llanelli
Merthyr v Aberavon
Newport v Bedwas
Pontypridd v RGC 1404
Swansea v Neath
Round 5: 29 September
Aberavon v Llandovery
Bedwas v Carmarthen Quins
Bridgend v Pontypridd
Cardiff v Bargoed
Cross Keys v Swansea
Llanelli v Newport
Neath v Ebbw Vale
RGC 1404 v Merthyr
