The 27 year-old former Sharks and Golden Lions back has played 76 Super Rugby matches and joins Ulster Rugby from French Pro D2 side Agen.
He won two Currie Cups in his three-year spell with the Sharks and was included in the Springboks training squad in 2008.
Speaking about his decision to join Ulster Rugby, Ludik said: "When I heard that there might be a chance to join Ulster I was very excited as it is a Province with a great history and proud fans.
"I watched a few Ulster games this season and I was really impressed by the passion and character that the team showed. The Ulster backline is packed full of top international players and it will be a challenge for me to try and break into the team.
"However, driving yourself to be better is what top-class rugby is all about and I hope that with hard work and determination that I will be able to play a big role for Ulster over the next two seasons."
Ulster's Director of Rugby, David Humphreys added: "With an increasing number of Ulster players involved in the Ireland international set-up it is important for us to continue to build a squad with strength in depth in all positions.
"Louis, as our final Non Irish Eligible signing for 2014/15 season, will add quality and provide experience to our young backline and his experience of Northern Hemisphere rugby in France over the past season means he is well prepared for the challenges of European rugby.
"We look forward to welcoming Louis and Chamé to Belfast and, as with many of our overseas players, look forward to watching him make an impact both on and off the field in Ulster."
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