The Mongolian Democratic Party (MDP) () was a political party in Mongolia that existed from 1990 to 1992. The MDP was the main opposition party from 1990 until 1992, when it merged with the Mongolian National Progress Party and founded the Mongolian National Democratic Party. The latter party later became a founding member of the modern-day Democratic Party.
By late November 1989, pro-democracy youth intellectual groups in Ulaanbaatar, inspired by the waves of revolution in Eastern Europe, began to criticize the government of the Mongolian People's Republic and the socialist one-party state. The Mongolian Democratic Union (MDU) was formed by the end of 1989 and would lay the foundations for Mongolia's first opposition political party during theà1990 revolution. On 18 February 1990, the MDU convened its first conference and established the Mongolian Democratic Party (MDP). Erdeniin Bat-ÃÂül was elected as the party's first and only chairman.
After the success of the 1990 revolution, the MDP held its first party congress on 8-9 April, during which it ratified its party charters and elected its officials. The MDP was officially registered as a legitimate political party by the Supreme Court of the Mongolian People's Republic on 7 April 1990, a day celebrated by the modern Democratic Party as the date of its first party congress and the start of its history.
In the subsequent 1990 elections, the country's first free and fair multi-party elections, the MDP would win 23 out of 430 seats in the representative People's Great Khural and 13 out of 50 seats in the newly established lower house, the State Little Khural. Therefore, making it the second-largest political party in parliament and the main opposition force against the ruling party.
After the ratification of a new constitution and the establishment of a unicameral parliament, the 1992 elections for the first State Great Khural were held on 28 June 1992. The MDP ran together with the Mongolian National Progress Party (MNPP) and the Mongolian Green Party, and won 4 out of 76 seats in the State Great Khural. In the same year, the MDP merged with the MNPP and the Mongolian Renaissance Party and founded the Mongolian National Democratic Party (MNDP) on 25 October.
The Democratic Union, an opposition coalition consisting mainly of the MNDP and the Mongolian Social Democratic Party (MSDP), would win 50 seats in the State Great Khural in the 1996 election, which was the first time the ex-communist Mongolian People's Revolutionary Party (MPRP) was out of power since 1921.
After the 2000 landslide victory of the MPRP, the opposition parties, including the MNDP, gained a total of 3 seats out of 76. On 6 December 2000, the MNDP would merge with the MSDP, the Mongolian Democratic Renaissance Party, and the Mongolian Religious Democratic Party, forming the modern-day Democratic Party ().