In the fictional Macross universe, Space War I (第一次星間大戦, Daiichiji Seikan Taisen) is the conflict that erupts between the forces of the U.N. Spacy (mankind's space force) and the alien Zentradi forces over possession of the SDF-1 Macross warship. The war lasts from 2009 until 2012 with significant destruction of the Earth's surface and 5 out of the 10 billion population losing their lives. The Zentradi are not without their losses as well. Supreme Commander Boddole Zer is destroyed along with 1.8 million of his fleet's ships by the combined forces of the U.N. Spacy, Earth's Grand Cannon, and the Zentradi that side with the humans after being considered "infected" with "Protoculture" (culture or activity other than fighting) by the Miclones (the Zentradi name for humans).
The phrase "Space War I" is used by the creators of Macross (Studio Nue) to denote the history and scale of the conflict, in the same way World War I (第一次世界大戦, Daiichiji Sekai Taisen) or World War II (第二次世界大戦, Dainiji Sekai Taisen) is in the real world.