The 24-year-old will join Liverpool on a free transfer at the end of the season.
Matip told Schalke’s official website: “I have always said that I would only leave Schalke to try something new and moving to another Bundesliga club was never an option.
“Although my decision was not easy, I am convinced that now is the right time to take this step.
“Schalke 04 will remain special to me. I was always proud to play for this great club and I will do everything possible in the coming months to get the most out of this season.”
Matip has featured for Cameroon at the 2010 and 2014 FIFA World Cup finals.