The announcements were made during Nintendo's latest Direct online broadcast, which focused on the two games but included a host of fresh announcements.
Arms, a fighting game in which a roster of characters fight using interchangeable, unique weapons grafted to their springy, elongated arms. It's super weird but very fun and launches worldwide on 16 June.
Splatoon 2, a sequel to one of the biggest hits on Nintendo's ill-fated Wii U console, is a colourful shooter starring squid-people called Inklings. In the game's core mode, teams compete to coat the majority of a given level's surface area in their colour of ink.
The anticipated online game is set to release on 21 July.
A co-op horde mode called Salmon Run was also announced for the game, as well as new Amiibo figures.
Other new Amiibo based on The Legend of Zelda and Super Smash Bros characters Cloud (from Final Fantasy), Corrin (from Fire Emblem) and Bayonetta (from... Bayonetta) were also announced.
The Zelda Amiibo will be released on 23 June with the Smash Amiibo following on 21 July.
There was also a ton of news regarding Nintendo's handheld 3DS console. To celebrate the 25th anniversary of Kirby, three new games were revealed. Team Kirby Clash Deluxe is free-to-play and out right now, Kirby's Blowout Blast is out this summer and a new multiplayer Kirby title is out towards the end of the year.
Nintendo also revealed the name of the new Pikmin title heading to 3DS for the first time. Hey! Pikmin is a 2D platformer heading to the handheld on 28 July.
The full Nintendo Direct as well as the Arms and Splatoon 2 segments are embedded below.