The Armed Forces of Mauritania (Arabic: الجيش الوطني الموريتاني, romanized: al-Jaysh al-Waṭanī al-Mūrītānī, French: Armée Nationale Mauritanienne) are the defense force of the Islamic Republic of Mauritania, having an army, navy, air force, gendarmerie, and presidential guard. Other services include the national guard and national police, though they both are subordinated to the Ministry of the Interior. As of 2018, the Mauritanian armed forces budget was 3.9% of the country's GDP.

The military forces of Mauritania were listed by the IISS Military Balance 2007 as comprising 15,870 personnel with an additional 5,000 paramilitaries, in the national gendarmerie. The Navy (Marine Mauritanienne) had 620 personnel and 11 patrol and coastal combatants, with bases at Nouadhibou and Nouakchott. The CIA reported that the navy included naval infantry. The small air force (Force Aérienne Islamique de Mauritanie, FAIM) had 250 personnel, 2 FTB-337 aircraft, 15 transport aircraft of various types, and 4 SF-260E trainers. The 5,000 paramilitaries were divided in the National Gendarmerie (3,000), and the National Guard (2,000) who both reported to the Ministry of the Interior. Other paramilitary services reported by the CIA in 2001 include the National Police, Presidential Guard (BASEP).

Saleh Ould Hanenna, a former army major, led the 2003 Mauritanian coup d'état attempt in June 2003. It aimed to overthrow President Maaouya Ould Sid'Ahmed Taya. He commanded a rebel section of the Army during two days of heavy fighting in Nouakchott. With the failure of the coup Hanenna initially escaped capture, and formed a group called the 'Knights of Change' with Mohamed Ould Cheikhna, but they were arrested on 9 October 2004.

General Mohamed Ould Abdel Aziz, a career soldier and high-ranking officer, was a leading figure in the 2005 Mauritanian coup d'état that deposed President Maaouya Ould Sid'Ahmed Taya.

In August 2008, General Ould Abdel Aziz led the 2008 Mauritanian coup d'état that toppled President Sidi Ould Cheikh Abdallahi. Following the latter coup, Abdel Aziz became President of the High Council of State as part of what was described as a political transition leading to a new election. He resigned from that post in April 2009 to stand as a candidate in the July 2009 presidential election, which he won. He was sworn in on 5 August 2009.

In March 1985, the Defense Intelligence Agency reported the army was 8,300 strong with no reserves (Military Intelligence Summary – Africa South of the Sahara, DDB 2680-104-85, ICOD 15 October 1984, Mauritania pages 4, 5, declassified by letter dated 29 April 2014). Reported regions at the time were Region I – Nouadhibou, Region II – Zoueirat, Region III – Atar, Region IV – formerly at Tidjikdja, which no longer existed, Region V – Nema, Region VI – Nouakchott, and Region VII – Rosso. The army was organized into the six regions which each supervised several companies, though there was 'one small autonomous infantry battalion stationed in Nouakchott.

The Army is 15,000 strong, according to the IISS, with six military regions, two camel corps battalions, one battalion of T-55 battle tanks, one armored reconnaissance squadron, eight garrison infantry battalions, seven motorized infantry battalions, one commando/para battalion, 3 artillery battalions, 4 air defense batteries, one engineer company, and one guard battalion. The 1ère région militaire is at Nouadhibou, 2nd Military Region is at Zouerate, 3rd Military Region is at Atar, 4ème région militaire may be at Tidjikdja, 5th Military Region headquarters is at Néma, The 6th Military Region may be in the area of the capital, and the 7th Military Region may be at Aleg.

The Mauritanian military is currently involved in Operation Enduring Freedom – Trans Sahara. Previous U.S. anti-terrorist engagement included training under the Pan Sahel Initiative. Under the PSI, a 10th Special Forces Group training team carried out a one-week border monitoring training programme in January 2004.