The Kurdistan Social Democratic Party (Kurdish: حزبی سۆسیال دیموکراتی کوردستان, romanized: Hizbî Sosyal Dîmukratî Kurdistan, abbreviated as KSDP) is a political party in Kurdistan Region. It was founded as Kurdistan Socialist Party - Iraq (Kurdish: حزبی سۆسیالیست کوردستان - عێراق, romanized: Hizbî Sosyalîst Kurdistan - Êraq, KSP-I). The first leader was Saleh Yousefi after 1981.

1979-1985, it was part of the short-lived alliance Kurdistan United Socialist Party (HSYK), which had included the Socialist Movement of Kurdistan as well as the two splinters of the South Kurdistan Movement and which birthed the Kurdistan Toilers' Party. The KSDP component in the alliance was split into two camps, the scientific socialist faction around Resul Mamend and the social democratic faction around Saleh Yousefi and Mahmoud Othman.^[1] Prior to the 1992 Kurdistan Region parliamentary election, it created an electoral alliance with the Kurdish Socialist Party (PASOK). In August, the Kurdistan Popular Democratic Party joined the alliance, and the three founded the Kurdistan Unity Party (KUP). A faction led by Resul Mamend refused to join the alliance and instead joined the Patriotic Union of Kurdistan in December 1992, where Mamend was included as member of the Political Bureau. The KUP joined the Kurdistan Democratic Party in August 1993.^[2]

A mere month later, a faction under Mohammed Haji Mahmoud broke away from the KDP again, re-establishing the KSP-I. The following year, it was renamed to Kurdistan Socialist Democratic Party (Kurdish: حزبی سۆسیالیست دیموکراتی کوردستان, romanized: Hizbî Sosyalîst Dîmukratî Kurdistan; Arabic: الحزب الاشتراكي الديمقراطي الكردستاني, romanized: Hizb al-Ishtiraki al-Dimuqrati al-Kurdistani).^[2] It had been known under this name until a recent name change, although the acronym KSDP stayed the same.

After 1992, the party was led by Mahmoud Othman. The party is currently led by Mohammed Haji Mahmoud.^[3]

In the 2013 Kurdistan Region parliamentary election the party got 12,501 votes (0.6%) and it won one seat in the Kurdistan National Assembly. For the 2024 Kurdistan Region parliamentary election, the party joined an electoral alliance together with the Kurdistan Communist Party – Iraq and the Kurdistan Toilers' Party. The alliance is called the Kurdistan Region Coalition.^[4]

The Kurdistan Socialist Democratic Party also has a paramilitary wing of Peshmerga soldiers under the direct command of party leader Mohammed Haji Mahmoud, whose nom de guerre is "Kaka Hama". The party's forces have fought in the Iraqi Civil War against the Islamic State of Iraq and the Levant (ISIL), mostly in the region south of Kirkuk. They also took part in the Mosul offensive (2016). Among the party fighters killed in combat against ISIL was Mohammed Haji Mahmood's son Atta.^[5]

There has been a developing rivalry between party leader Mohammed Haji Mahmoud and his brother Ebdulla Haji Mahmoud. Ebdulla was first a MP in the Kurdistan Region Parliament and is currently the "Minister of Martyrs and Anfal". He lost some influence in the party after a party congress in March 2023, where Mohammed's son Rêbîn replaced him in the office for public relations and replaced a lot of the staff with associates of him.^[6]

In late January 2024, the rivalry reemerged over a dispute whose son would become president of the Baxtiyarî Sports Club in Silêmanî. The situation escalated and shots were exchanged.^[7] On February 14, Selah Elî, who was a close associate of Ebdulla was replaced with Husên Xelîfe as leader of Peshmerga affairs, an associate of Mohammed. During the tensions, Elîs son reportedly opened fire, which led security forces to intervene.^[8]

On the 5th of March, an assembly led by Mohammed Haji Mahmoud decided to strip Ebdulla of the seat of the co-chair as well of his party membership, calling on him to give back properties owned by the party. Ebdulla rejected the decision, arguing that only a proper party congress could make such a decision. According to the news network Peregraf, the conflict between the brothers had been going on for two years.^[9]