The wren is a tiny brown bird, although it is heavier and not as slim as the even smaller goldcrest. It is dumpy, almost rounded, with a fine bill, quite long legs and toes, very short round wings and a short, narrow tail which is sometimes cocked up vertically. For such a small bird it has a remarkably loud voice.

It is the most common UK breeding bird, although it suffers declines during prolonged, severely cold winters.