The versatile back picked up the club's Player of the Month accolade in September after a fine start to the new Guinness PRO12 season but is out until the end of November with a fractured cheek bone.
Despite the injury, he was delighted to tie his future down with Ulster.
"I'm thrilled to be extending my stay at Ulster," said Ludik. "Myself and my family really enjoy Belfast and we feel very much at home here.
"Everything about Ulster Rugby is first class; the stadium, the training facilities, the players and coaches, the medical care and the supporters.
"There is a brilliant vibe amongst the squad and everyone is working hard to try to achieve success this season.
"Once I return to fitness, I'm looking forward to contributing to the team this season and for the following three years."
Director of rugby Les Kiss was delighted to extend Ludik's stay with the club and praised the impact the 30-year-old has had on and off the field.
"Keeping Louis on our roster is a major boost for us. He is an outstanding guy who gives 100 per cent to the cause and adds so much value both on and off the pitch," he said.
"He is a great influence on the squad and he also does some great work in the local community.
"His form at the start of this season has been absolutely brilliant and I'm looking forward to seeing him deliver for us over the next few years."
Guinness PRO12 Ulster News
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