The Hungarian Communist Party (Hungarian: Magyar Kommunista Párt, pronounced [ˈmɒɟɒr ˈkomːuniʃtɒ ˈpaːrt], abbr. MKP), known earlier as the Party of Communists in Hungary (Hungarian: Kommunisták Magyarországi Pártja, pronounced [ˈkomːuniʃtaːk ˈmɒɟɒrorsaːɡi ˈpaːrcɒ], abbr. KMP), was a communist party in Hungary that existed during the interwar period and briefly after World War II.

It was founded on November 24, 1918, as Party of Communists in Hungary, and was in power between March and August 1919 when Béla Kun ran the short-lived Hungarian Soviet Republic. The communist government was later overthrown by the Romanian Army, Kun was exiled to Vienna and later he and many other communists moved to Moscow. During those years, membership was becoming smaller every year. During World War II the party changed its name to the Peace Party, but only a year later in 1944, they embraced a new name which they would hold until 1948. After the war, they regained power, and their membership rose up quickly, which led to Mátyás Rákosi suppressing other parties in the country besides the social democrats (which were aligned with them) to form a one-party state. In 1948, the party merged with the social democrats to form the Hungarian Working People's Party which became the next ruling party of Hungary. It was also a member of Comintern and its successor Cominform.

The Communist Party of Hungary (KMP) was first established as The Party of Communists in Hungary in late 1918 by Béla Kun, a former journalist who fought for Austria-Hungary in World War I. After spending time in a Russian POW camp, Kun, along with several associates, set up the initial workings of the KMP in the downtown of Moscow in October 1918. These first members returned to Hungary in November, and on the 24th officially created the KMP. The Communist Party chose "The Party of Communists in Hungary" (Hungarian: Kommunisták Magyarországi Pártja) as its name, instead of "Hungarian Communist Party", since the vast majority of its represented social class, the factory workers, still did not have ethnic Hungarian roots in Budapest, and ethnic Hungarians were only a minority in the newly founded party. Initially, the group was small in number and boasted only its founders and a handful of leftist Social Democrats. Nonetheless, the political instability of the government under Mihály Károlyi and the growing popularity of the Bolshevik movement prompted the Social Democrats to seek a coalition with the KMP. For the Social Democrats, an alliance with the KMP not only increased its standing with the common people but also gave it a potential link to the increasingly powerful Russian Communist Party, as Kun had ties with prominent Russian Bolsheviks.

After the establishment of the Hungarian Soviet Republic in March 1919, Kun set about nationalising private industry while embarking on a massive agricultural collectivization project. He also took steps towards normalising foreign relations with the Triple Entente powers in an effort to gain back some of the land that Hungary was set to lose in the postwar negotiations. For the 133 days that the Hungarian Soviet Republic existed, the KMP concentrated mostly on trying to fix the widespread economic chaos that had resulted from Hungary's defeat in World War I. Unfortunately, Kun's economic policy created higher inflation and led to food shortages across the land. Opposition began to grow, led by Miklós Horthy, and in June, an attempted coup made the KMP launch a violent terror campaign through its secret police. The Soviet Republic fell on August 1, 1919, after the Hungarian Army's crushing defeat by Romania. The invading Romanians seized Budapest from the Communists, exiled Kun to Vienna and forced the KMP to hand over power to the Social Democrats.

The fall of the Soviet Republic was followed by a year-long anticommunist purge, known as the White Terror, by the new nationalist government under István Bethlen in which anywhere from 1,000 to 5,000 people were killed, and thousands more were imprisoned and tortured. Much of the old KMP leadership was executed or exiled, primarily to Vienna. There, remnants of the KMP Central Committee, once again led by Kun, reformed into a Provisional Central Committee, which attempted to keep the party together despite its illegal status in Hungary.

Throughout the 1920s, many Hungarian Communists moved to Moscow, with Kun among them. Kun's actions in Russia, most notably the organization of a massacre of White Russian prisoners-of-war in 1921, drew censure from the Soviet leader Vladimir Lenin and other prominent Bolsheviks. Nonetheless, Kun maintained a prominent position with Comintern until 1937, when he was arrested and executed during one of Joseph Stalin’s purges. Furthermore, Kun was the unquestioned leader of the KMP during the interwar period, with his main rival, Jenő Landler, dying in 1927.

The party also organised a legal cover party, the Socialist Workers Party of Hungary (MSzMP), to act as its representative in Hungary. However, the Hungarian government soon took steps to abolish the MSzMP, and by 1927, the party existed in name only.

For the remainder of the interwar period, the internal leadership of the KMP beyond Kun fluctuated tremendously, and membership was minuscule. After the deadly derailment of a passenger train at Biatorbágy by Szilveszter Matuska in 1931, the government declared martial law and used the opportunity to arrest suspected communists. Two of those arrested, and the leading party members Imré Sallai and Sándor Fürst, were executed the following year. The KMP was damaged to the point that the Comintern dissolved it in 1936.