The Wairau by-election 1872 was a by-election held in the Wairau electorate during the 5th New Zealand Parliament, on 19 February 1872. The by-election was caused by the resignation of incumbent MP William Henry Eyes and was won by Arthur Seymour, who defeated Joseph Ward. Both candidates were prominent Marlborough politicians, and for both of them, this was their first attempt at election to the General Assembly.