Ghadir (Persian: غدیر, pronounced [ɣædiːɾ]; named after the Ghadir Khumm) is a class of midget submarines built by Iran specifically for cruising within the shallow waters of the Persian Gulf. The Islamic Republic of Iran Navy is the sole operator of this class, whose submarines all serve in the Southern Fleet. No submarine of this class is active at the Northern Fleet, i.e., the Caspian Sea.

Iran had shown interest in midget submarines in the 1980s. According to the Conway's All The World's Fighting Ships, Iran assembled a midget in Bandar Abbas that was completed in 1987 in an unsuccessful attempt. Iran reportedly purchased a second midget of another design from North Korea, delivered in 1988. It is alleged that by 1993, nine midget submarines –able to displace 76 tons surfaced and 90 tons submerged, with a top speed between 8 knots (15 km/h; 9.2 mph) and 12 knots (22 km/h; 14 mph)– were imported from North Korea.

The existence of Ghadir class was first known in February 2004. An unclassified 2017 report by the U.S. Office of Naval Intelligence stated that Iran purchased at least one Yono class submarine from North Korea in that year.

In May 2005, Iran announced that it has started mass production of its own indigenous midget submarines, and aired footage of one cruising surfaced on television. Later that month, the submarine was tested during the third phase of military exercise Ettehad 84. In November 2007, commander of the IRIN Commodore Habibollah Sayyari said the second boat in the class had been completed after ten years of construction. Iranian supreme leader Ali Khamenei was quoted saying to Iran's navy commanders on the day the submarine was launched: "Today, you have been able to design and build many of the military requirements. We have become self-sufficient from other countries."

In May 2014, submarine Ghadir 953 cruised in the Indian Ocean to make a port call to Karachi, Pakistan along with a naval group consisting of Falakhon, Khanjar, Hendijan and Deylam, participating in a joint drill with Pakistan Navy vessels.

Sources are inconsistent about the class which Ghadir submarines are derived from. When it was first unveiled, some experts pointed out that it is similar in appearance to Yugo-class submarines, while others said that they were about 1.5 times larger than the Yugos, and more similar to the Sang-O class. Other sources say they are based on the Yono class. Ghadir submarines displace 117 tonnes (115 long tons) surfaced, and 125 tonnes (123 long tons) submerged. The class design is 29 m (95 ft 2 in) long, would have a beam of 9 m (29 ft 6 in) and a draft of 8.2 m (26 ft 11 in). The submarines have a maximum surface speed of 10 knots (19 km/h; 12 mph) and a maximum submerged speed of 8 knots (15 km/h; 9.2 mph). They have a secondary retractable propeller are powered by diesel–electric machinery, and fitted with two 533 mm (21 in) torpedo tubes.

Submarines in the class are equipped with sonars of an unknown type. Ghadirs have a crew of seven.

Ghadir submarines are said to have launched Valfajr and Hoot torpedoes. Anti-ship cruise missiles Nasr-1 and Jask-2 are both reportedly launched successfully, the latter being developed specifically for launch from submarines. The ships in the class are also capable of laying naval mines in addition to retrieving frogmen for special operations. They are assumed to have "an extremely limited endurance", and are described as "very maneuverable" and able to "sit silently submerged while waiting for its prey". Considering that Ghadir submarines could carry only two torpedoes or missiles, Joseph Trevithick writes that Iranians may plan to use them "en masse to launch barrages of the missiles".