Mohammed Ibrahim Hassan al-Sinwar (Arabic: محمد إبراهيم حسن السنوار, romanized: Muḥammad Ibrāhīm Ḥasan as-Sinwār; 16 September 1975 – 13 May 2025) was a Palestinian politician and militant who became the third Hamas leader in the Gaza Strip, following the killing of his brother, Yahya Sinwar in October 2024. He also served as the seventh commander of the Al-Qassam Brigades since July 2024. He held both positions until he was killed by the Israel Defense Forces (IDF) in May 2025.

Born in the Khan Yunis refugee camp, Sinwar spent several years in Israeli and Palestinian Authority jails in the 1990s and became the leader of Hamas's Khan Yunis Brigade in 2005. Israel attempted to assassinate him several times prior to killing him in May 2025.

Mohammed Ibrahim Hassan Sinwar was born in the Khan Yunis refugee camp on 16 September 1975. Sinwar's family fled from Al-Majdal Asqalan (Ashkelon) during the 1948 Arab–Israeli War.

Sinwar joined Hamas in 1991, becoming a member of its military wing, the Al-Qassam Brigades. He was ideologically influenced by Hamas co-founder Abdel Aziz al-Rantisi. His rank in the group rose over time, and he eventually became one of its joint chief of staffs, where he became close to Hamas commanders such as Mohammed Deif and Sa'ad al-Arabid—the latter was assassinated in 2003. He also became close to deputy Hamas commander Marwan Issa.

Sinwar partook in the First Intifada. Israel arrested him in 1991 and accused him of "terrorism", but released him nine months later from the Ktzi'ot Prison. In 1992, he was allegedly involved in an attempt to capture and kill an Israeli soldier (Alon Karavani), an operation led by Deif. He was arrested by the Palestinian Authority in Ramallah later in the 1990s, spending three years in jail before escaping in 2000.

During the Second Intifada, Sinwar planned attacks against Israeli targets and oversaw rocket attacks. In 2005, he became the commander of Hamas's Khan Yunis Brigade—a role he held until 2016, according to the IDF. He operated alongside senior commanders such as Hassan Salameh [ar; he], and accumulated experience and influence because he was able to stay under the radar. Little was known about him by Israel's security services, and Arab officials said that he mostly operated "behind the scenes", giving him the nickname "Shadow".

Sinwar reportedly established ties with criminal clans, such as the Doghmush clan, facilitating the 2006 abduction of Israeli soldier Gilad Shalit. He was a part of the cell that conducted the abduction, being a key architect of the raid. He also played a key role in concealing Shalit, allegedly briefly holding the soldier captive himself. Shalit was exchanged in 2011 for 1,027 Palestinian prisoners, including Sinwar’s brother, Yahya Sinwar, with Mohammed insisting upon his release.

Sinwar reportedly convinced the al-Qaeda-aligned Ansar Bait al-Maqdis to join the Islamic State, which established the group's Sinai Province. Hamas provided the group with weapons and training in exchange for the group ensuring that arms shipments reached Gaza. He further gained influence after Raed al Atar and Muhammad Abu Shamaleh [ar; he], who were candidates to replace Deif, were killed during the 2014 Gaza war.