The Welsh League Division One is the second tier of the Welsh football pyramid for clubs from south Wales.
North and mid-Wales has the parallel Huws Gray Alliance.
At the end of the season the champions of both second tier leagues are eligible for promotion to the Welsh Premier, if they can gain the FAW's domestic club licence. If not, the runner-up may also qualify.
Teams that have gained promotion from the Welsh League in recent years are Barry Town United (2017), Cardiff Met (2016), Haverfordwest County (2015), Afan Lido (2011), Neath FC (2007), Grange Harlequins (2005), Llanelli (2004), Port Talbot (2000), Haverfordwest County (1997 and 2015) and Carmarthen Town (1996).
The league has operated with a reduced number of 16 clubs since season 2010/11.
Llanelli Town won the title in 2017/18 to secure a return to the WPL.
Afan Lido, Briton Ferry Llansawel (as Briton Ferry), Grange Quins, Llanelli and Ton Pentre are previous members of the Welsh Premier.