Saints land Bees keeper
By Simon Fudge
Last Updated: 01/01/70 1:00am
The 24-year-old completed a medical at St Mary's on Tuesday and agreed terms on a four-and-a-half year deal with the South Coast club.
Smith, who had attracted the interest of Premiership sides Portsmouth and Tottenham Hotspur in recent months, revealed that it was his desire to join Gordon Strachan's side instead.
"This was really where I wanted to be. The sheer size of the club is impressive from the stadium to the training ground where the facilities are first class," Smith told Southampton's official website.
"I came here a few weeks ago to train and I was very impressed by what Southampton had to offer and by their goalkeeping coach David Coles.
"He worked us hard but I have no problem with that because I am here to learn and improve.
"There were a few teams watching me but it was not too unsettling even though I knew I wanted to play in The Premiership.
"I knew Brentford were looking to move me on because they needed the money so I just kept my focus on doing well for them so that the watching clubs would not lose interest in me."
Smith is expected to travel with the Saints squad on Saturday, when they visit Manchester United at Old Trafford in The Premiership, where he is likely to back up number one Antti Niemi.