The First Shinobi World War (第一次忍界大戦, Daiichiji Ninkai Taisen, English TV: First Great Ninja War), or simply the Shinobi World War (忍界大戦, Ninkai Taisen, English TV: Great Ninja War), was the first major conflict to occur among the Five Great Shinobi Countries. The war's outbreak plunged the world into a chaos not seen since the end of the Warring States Period, for which reason there are very few records about the war. According to Ōnoki, the war was a result of countries and their hidden villages taking resources from other countries and other hidden villages; Madara Uchiha's demand that Iwagakure be subservient to Konohagakure is implied to be the first such example of this.
In the lead up to the war, Konoha's First Hokage, Hashirama Senju, distributed the tailed beasts to the other hidden villages, something that was discussed and agreed upon at the first ever Kage Summit. Hashirama and his fellow Kage hoped that dividing the tailed beasts among their villages would create a power balance, thus establishing peace between them. Although this did bring an end to smaller wars, conflicts of the era began to escalate and Hashirama ultimately died in battle. His successor as Hokage, Tobirama Senju, attempted to continue Hashirama's pursuit of peace, but even his efforts could not stop the beginning of the First Shinobi World War. Tobirama would go on to die during the war, killed in battle with Kumogakure's Kinkaku Force; he acted as a decoy so that his subordinates could escape. Before he died, Tobirama appointed one of his students, Hiruzen Sarutobi, to be the next Hokage.
The war took a heavy toll on the Five Great Shinobi Countries, badly damaging each of them. In the end, an armistice treaty was signed, establishing twenty years of peace between them; the peace was ended by the start of the Second Shinobi World War. Combat tactics developed during the war would have the most lasting impact, with experiences from the war still shaping how ninja do battle in the modern era. After the war, Konoha established the Memorial Stone, upon which it engraved the names of all ninja to die in the village's service.
- The conclusion of the First Shinobi World War mirrors the events that followed the real-life First World War. World War I was ended with armistice, before a treaty was finally signed. In addition, virtually all countries on the European continent (the primary setting of the war) were completely devastated in some manner by the time hostilities ended. Nevertheless, within twenty years after the signing of the treaty, World War II would begin.