Waikouaiti was a parliamentary electorate in the Otago region of New Zealand, from 1866 to 1908.

The electorate is named after the township of Waikouaiti, which is close to the Waikouaiti River.

The Waikouaiti electorate was formed for the 1866 election.^[1] William Murison was elected as the first representative, narrowly beating later Premier Julius Vogel;^[2] Vogel stood some weeks later in the Gold Fields electorate and was successful there.^[3] Murison resigned in 1868.^[4] The resulting 1868 by-election was won by Robert Mitchell, who in turn resigned before the end of the term in the following year.^[5] He was succeeded by Francis Rich, who won the 1869 by-election and served until the end of the term in 1870, when he retired.^[6]

George McLean won the 1871 election and resigned again in the following year.^[7] McLean was succeeded by David Monro, who won the 1872 by-election and resigned one year later. Monro had been a member of all previous Parliaments.^[8] Monro was succeeded by John Lillie Gillies, who won the 1873 by-election and resigned in 1875.^[9] Gillies was succeeded by McLean, who successfully stood for re-election in the 1875 by-election. McLean was confirmed in the general elections of 1875 and 1879 election; he retired at the end of the parliamentary term in 1881.^[7]

James Green, who had previously represented Port Chalmers, succeeded McLean in the 1881 election.^[10] Green was defeated in the 1884 election by John Buckland.^[11] In the 1887 election, Buckland stood in Waihemo and was defeated there.^[12]

James Green was re-elected in 1887 in the Waikouaiti electorate and represented it for several terms until he was defeated in the 1896 election by Edmund Allen who stood for the Liberal Party.^[13] In the 1902 election, Allen successfully contested the Chalmers electorate.^[14]

Thomas Mackenzie was elected in the Waikouaiti electorate in 1902 and would represent it until the electorate's abolition in 1908, when he was elected for Taieri.^[15] Mackenzie would later become Prime Minister.^[16]