Fate of Worlds: Return From the Ringworld is a science fiction novel by American writers Larry Niven and Edward M. Lerner. It was first published in hardcover and ebook editions by Tor Books in August 2012, with paperback and trade paperback editions following from the same publisher in July 2013 and June 2014, respectively. It is the fifth and final book in the Fleet of Worlds series, itself a subset of Niven's Known Space series.