The 31-year-old, who has played 68 Tests, 166 one-dayers and 64 T20 internationals, will be available for all formats from April until late July.
"To sign a player of that quality for as long as we have is a great coup," head coach Mark Davis told BBC Sussex.
"He is a very exciting signing. We were keen to get hold of him the moment we saw he was available."
Taylor has scored 5,197 Test runs at an average of 45.99, with his highest score of 290 coming in the second Test against Australia last month, which ended as a draw.
"He has captained his country and has a great record," Davis added.
"He will add to us as a team on and off the pitch and be a positive influence. He will be a great help to our new captain Luke Wright and our batsmen."
Taylor previously played T20 cricket in England for Durham in 2010.
Sussex have been able to move for Taylor because Australian pace bowler Steve Magoffin is set to qualify as a non-overseas player.
Magoffin, 36, has an English wife and has applied for a UK passport.
Sussex have signed New Zealand batsman Ross Taylor as their overseas player for the first half of the 2016 season.