It is scheduled to be released in North America and United Kingdom on July 20, 2018 by Universal Pictures, ten years to the month of the original film's release.

When is mama mia here we go again coming out? Okie... think carefully first, then make a decision:
To answer this question, we should know that: It is scheduled to be released in North America and United Kingdom on July 20, 2018 by Universal Pictures, ten years to the month of the original film's release. So, the answer is July 20 , 2018.