Pure Legal Ltd will be the name on the club's eye-catching lime green Nike branded away shirt.
The sponsors managing director Phil Hodgkinson said: "Southport FC have been my local club since I moved to the area 22 years ago.
"Pure Legal Ltd is based in Prescot. We are a new brand that offers transparency, no cold calls and quality of service to the general public.
"Southport's tremendous FA Cup run last season culminating at Derby County in the Third Round, the BT Sports coverage of live matches and highlights package attracted us as a firm. The Vanarama National League is very high profile.
"The new away shirt looks fantastic and will take our name all around the country.
"I am really looking forward to the season ahead and being a sponsorship partner to an excellent football club.”
Southport FC chairman Charlie Clapham said: "I am delighted to introduce Pure Legal Ltd as our new shirt sponsors.
"This is a fantastic sponsorship joining our ever growing business / commercial family of partnerships taking Southport Football Club forward.
"Our new away shirt looks a real winner.”