Kaisen: Outbreak (開戦～Outbreak～) was a professional wrestling event produced by the Wrestle-1 promotion (W-1), that took place on March 2, 2014, at Ryōgoku Kokugikan in Tokyo, Japan. For the event – W-1's first at Ryōgoku Kokugikan – the promotion collaborated with American promotion Total Nonstop Action Wrestling (TNA), the first of two W-1/TNA joint events in 2014.

Wrestle-1 was a Japanese puroresu or professional wrestling promotion, founded in July 2013 by Keiji Mutoh following his resignation from All Japan Pro Wrestling (AJPW). The core of the promotion's roster was formed by wrestlers loyal to Mutoh, who left AJPW in a mass exodus during June 2013. Mutoh served as the promotion's first president and the head of its parent company, kabushiki gaisha named GEN Sports Entertainment. In March 2017, Kaz Hayashi took over as the new president of Wrestle-1. The promotion held its first event on September 8, 2013, at Tokyo Dome City Hall.