对牛弹琴（拼音：duì niú tán qín）是一个汉语成语，最早出自汉代牟融撰写的《理惑论》。该成语比喻对不讲道理的人讲道理，对不懂得美的人讲风雅，也用来讥讽人讲话时不看对象。
Playing the Harp to an Ox
One day Gong Mingyi, the celebrated musician, was playing an elegant tune on his harp to amuse a browsing ox.
The ox, however, continued to munch, paying no heed to him at all.
Then he struck up some different notes, which sounded like mosquitoes droning and calves bleating. Whereupon the ox flicked its tail, pricked up its ears, and began frisking round and round, evidently absorbed in the music.