Reds have signed defender Ryan Dickson, who joins the club after spending last season at Colchester United on a two-year contract.
The 27-year-old came through the ranks at his local club Plymouth Argyle.
He turned professional in 2004 but during his four years with the Pilgrims struggled to break into the side.
He had loan spells with neighbours Torquay United.
Ryan spent the 2007-08 season on loan at Brentford where he impressed enough to sign a permanent contract with the club.
He went on to spend two years at Griffin Park and appeared 96 times for the Bees.
It was this form that led to a move to Southampton in 2010.
During his time at the Saints he played alongside the likes of England duo Rickie Lambert and Adam Lallana.
Ryan appeared 23 times for the Saints, scoring once, but following the arrival of Danny Fox was forced down the pecking order under Nigel Adkins.
A loan spell with Yeovil Town followed where the left back scored once in five appearances before enjoying a similar stint with Leyton Orient.
In 2013, Ryan headed north to play for Bradford in a temporary switch before signing a one-year-deal at Colchester United last summer after a trial at Plymouth.
He finished the campaign with 35 appearances to his name and has made more than 200 appearances in his professional career.
Ryan is John Gregory’s third summer signing following the captures of midfielder Jimmy Smith and goalkeeper Brian Jenson.
Ryan said: “I’m delighted to be at Crawley working for a highly-
respected manager at an ambitious club.
“I know this league well and I definitely feel the club is capable of challenging for the play-offs next season.
“It’s a really exciting new challenge for me and I can’t wait for it to start.”
John Gregory said: “I was really impressed with Ryan when I saw him on a number of occasions last season. Several clubs at our level were keen to sign him but he’s excited about what we are trying to build at Crawley and I think he is going to be a very good addition to our squad.
He’s a very solid defender who is an excellent athlete and I’m sure our fans will enjoy watching him play.”