The Acacia class was a class of twenty-four sloops that were ordered in January 1915 under the Emergency War Programme for the Royal Navy in World War I as part of the larger Flower class which were also referred to as the "Cabbage class", or "Herbaceous Borders". They were ordered in two batches, twelve ships on 1 January and another twelve on 12 January, and all were launched within about four or five months, and delivered between May and September 1915. They were used almost entirely for minesweeping until 1917, when they were transferred to escort duty.
They were single-screw fleet sweeping vessels (sloops) with triple hulls at the bows to give extra protection against loss when working.
Iris — built by Lobnitz, launched 2 June 1915. Sold 26 January 1920, becoming mercantile Principe d'Asturias.
Jonquil — built by Charles Connell and Company, Scotstoun, launched 12 May 1915. Sold May 1920 in Portugal, becoming Portuguese warship NRP Carvalho Araújo, classified as a cruiser, discarded 1959.
Lily — built by Barclay Curle, launched 16 June 1915. Depot ship October 1923, renamed Vulcan II; renamed Adamant II in 1930. Sold for breaking up 25 June 1930.
Magnolia — built by Scotts, launched 26 June 1915. Sold for breaking up 2 July 1932.
Mallow — built by Barclay Curle, launched 13 July 1915. Transferred to Royal Australian Navy in July 1919, dismantled July 1932, sunk as target off Sydney 1 August 1935.