War of the Worlds (2019) was a professional wrestling tour co-produced by the American Ring of Honor (ROH) and Japanese New Japan Pro Wrestling (NJPW) promotions. The tour's four events took place on May 8 at the Buffalo RiverWorks in Buffalo, New York, May 9 at the Ted Reeve Arena in Toronto, Ontario, Canada, May 11 at the DeltaPlex Arena in Grand Rapids, Michigan and May 12 at the Odeum Expo Center in Chicago, Illinois. The first night would be taped for future episodes of ROH's weekly television program, Ring of Honor Wrestling, while the second night aired live on pay-per-view (PPV), while also being broadcasted by ROH and NJPW's streaming services Honor Club and NJPW World and Fite TV. 2019 was the sixth year in which ROH and NJPW co-produced events under the War of the Worlds name.
In 2014, Japanese promotion New Japan Pro-Wrestling (NJPW) and Ring of Honor (ROH) formally forged a relationship, which saw them present the first War of the Worlds show on May 17, 2014, at the Hammerstein Ballroom in New York City, New York. The following year, War of the Worlds was held over two days at the 2300 Arena in Philadelphia, Pennsylvania and in 2016 it was expanded to a three-show tour with shows taking place in Dearborn, Michigan, Toronto, Ontario and New York City and later it was expanded to a four day tour. The 2018 War of the Worlds tour was officially announced in January 2018, when ROH put tickets on sale for the events. These marked the fifth annual shows co-promoted by NJPW and ROH.
The War of the Worlds tour featured professional wrestling matches that involved different wrestlers from pre-existing scripted feuds and storylines. Wrestlers portrayed villains, heroes, or less distinguishable characters in the scripted events that built tension and culminated in a wrestling match or series of matches.