Burn the midnight oil Informal

To work or study late into the night, typically to meet a deadline or finish something important.

Unlike “burn the candle at both ends,” which implies exhausting oneself across several fronts, this phrase focuses narrowly on the act of staying up specifically to get work done — the effort is usually seen as purposeful rather than reckless.

The phrase refers to the oil lamps used for lighting before electricity, when working after dark meant literally burning oil to see. Its earliest known appearance is in Francis Quarles’s 1635 collection “Emblems”: “We spend our midday sweat, our midnight oil.” A century later, John Gay used the same image in his 1727 fable “The Shepherd and the Philosopher,” asking, “Hath thy toil o’er books consumed the midnight oil?” The verb “burn” itself only became standard in the phrase during the 19th century, once “midnight oil” had already been established for two hundred years as shorthand for late-night intellectual labor.

She had to burn the midnight oil all week to finish the grant proposal on time.

I don’t mind burning the midnight oil once in a while, but three nights in a row is too much.

The whole team burned the midnight oil before the product launch.

A: “Why do you look so tired?” B: “I’ve been burning the midnight oil trying to finish my thesis.”