During the era before the hidden villages, ninja wore armour that was similar to that of samurai. Dating back to at least Indra Ōtsutsuki's era, it boasted a higher defence than the simple stealth-orientated clothing that the shinobi would wear on missions that stressed concealment over combat. Shinobi in Konoha continued to wear the armour until at least the First Shinobi World War, when in the second the transition into flak jackets began.
The Akimichi clan of Konohagakure seems to have persisted in the use of armour, sometimes even combining it with the current flak jackets. Hiruzen Sarutobi had a small custom set of armour that gave him far more flexibility on top of a kabuto helmet over the usual plate armour.