一石二鳥 (Isseki nichō)

Literally: One stone, two birds

Example: “図書館で勉強すれば静かだし、本も借りられるので一石二鳥だ。” — Studying at the library is quiet and I can borrow books too: two birds with one stone.

English equivalent: To kill two birds with one stone

Origin: A Japanese rendering of the English "kill two birds with one stone." The English saying turns up in English–Japanese dictionaries at the end of the Edo period; in the Meiji era it was translated as isseki o motte nichō o korosu ("with one stone, kill two birds"), and in the Taishō era (1912–1926) it was shortened to today's four characters. So although it looks like an old Chinese idiom, it comes from English. Japanese also has an older four-character phrase with the same meaning, ikkyo ryōtoku ("one move, two gains").