Disanayaka Mudiyanselage Jayaratne (Sinhalese: දිසානායක මුදියන්සේලාගේ ජයරත්න,Tamil: திசாநாயக்க முதியன்சேலாகே ஜயரத்ன; born 4 June 1931) known as D. M. "Di Mu" Jayaratne is a veteran Sri Lankan politician who was Prime Minister of Sri Lanka from 2010 to 2015. A founding member of the Sri Lanka Freedom Party, Jayaratne was first elected to parliament in 1970. He was sworn in as Prime Minister on 21 April 2010.
Jayaratne first entered parliament following the 1970 general election, obtaining 14,463 votes as the Sri Lanka Freedom Party (SLFP) candidate in the Gampola electorate, and defeating W.P.B. Dissanayake of the United National Party (UNP). He was subsequently defeated by Dissanayake in the 1977 election in which just 8 members of the SLFP were returned to parliament. He was again re-elected to parliament in 1989 from the Kandy District under the new preferential voting system. He obtained 54,290 preferential votes, topping the SLFP list in the Kandy District.
Following the election victory of the United People's Freedom Alliance at the 2010 general election, Jayaratne, the most senior member of the SLFP, was sworn in as Prime Minister on 21 April 2010. Under the constitution of Sri Lanka, the Premiership is largely a ceremonial post. Along with it, he also held the Ministry of Buddha Sasana (Buddhism) and Religious Affairs.