Sonic Forces is a developed by and published by . Produced in commemoration of the 25th anniversary of the franchise, it was released for , , , and in November 2017. The story sees joining a resistance force to stop , who has by 99% alongside new villain Infinite. It features three gameplay modes: "Classic", gameplay similar to the original Sonic games; "Modern", 3D gameplay similar to (2008) and (2010); and a mode featuring the "Avatar", the player's .
The game was primarily developed by staff who had worked on Sonic Colors and , using an updated version of the Hedgehog Engine, used in Sonic Unleashed and Generations. Development began after the release of in 2013. The game was intended to have a darker tone compared to previous entries in the franchise, and the character creation system was inspired by Sonic fan art the developers had come across over the years. It was announced, alongside , under the working title of Project Sonic 2017 during the Sonic 25th anniversary event at the 2016 .
Sonic Forces received mixed reviews from critics. They praised its presentation, music, voice acting, character creation system, and the Modern Sonic gameplay, but criticized the plot, overly scripted level design and gameplay, technical problems, short length, the inclusion of Classic Sonic, and Infinite’s underdeveloped characterization. Many critics called it a disappointment in the wake of the positively received Sonic Mania, released earlier that year. The critical feedback influenced the development of the Sonic series' next entry, (2022).