Khandoba (IAST: Khaṇḍobā), also known as Martanda Bhairava and Malhari, is a Hindu deity worshiped generally as a manifestation of Shiva mainly in the Deccan Plateau of India, especially in the state of Maharashtra and North Karnataka. He is the most popular Kuladevata (family deity) in Maharashtra. He is also the patron deity of some Kshatriya Marathas (warriors), farming castes, shepherd community and Brahmin (priestly) castes as well as several of the hunter/gatherer tribes that are native to the hills and forests of this region.

The sect of Khandoba has linkages with Hindu and Jain traditions, and also assimilates all communities irrespective of caste, including Muslims. The sect of Khandoba as a folk deity dates at least to 12th century. Khandoba emerged as a composite god possessing the attributes of Shiva, Bhairava, Surya and Kartikeya (Skanda). Khandoba is sometimes identified with Mallanna of Telangana and Andhra Pradesh and Mailara of Karnataka.

Khandoba is depicted either in the form of a linga, or as an image of a warrior riding on a horse. The foremost centre of Khandoba worship is the Khandoba temple of Jejuri in Maharashtra. The legends of Khandoba, found in the text Malhari Mahatmya and also narrated in folk songs, revolve around his victory over demons Mani-malla and his marriages.

The name Khandoba comes from the words khadga (sword), the weapon used by Khandoba to kill the demons, and the suffix ba (father). Another name Khanderaya means "king Khandoba". Another variant is Khanderao, where the suffix rao (king) is used. In Sanskrit texts, Khandoba is known as Martanda Bhairava, a combination of Martanda (an epithet of the solar deity Surya) and Shiva's fierce form Bhairava. The name Mallari or Malhari is split as Malla and ari (enemy), thus meaning "enemy of the demon Malla". The Malhari Mahatmya records Martanda Bhairava, pleased with the bravery of Malla, takes the name "Mallari" (the enemy of Malla). Other variants include Malanna (Mallanna) and Mailara (Mailar). Other names include Khandu Gavda, Mhalsa-kant ("husband of Mhalsa") and Jejurica Vani.

In a popular oleograph representation of Khandoba, Mhalsa is seated in front of Khandoba on his white horse. Mhalsa is piercing a demon's chest with a spear, while a dog is biting his thigh and the horse is hitting his head. The other demon is grabbing the reins of the horse and attacking Khandoba with a club as Khandoba is dismounting the horse and attacking the demon with his sword. In other representations, Khandoba is seen seated on a horse with the heads of demons trod under the horse's hooves or their heads under Khandoba's knees.

In murtis (icons), Khandoba or Mailara is depicted as having four arms, carrying a damaru (drum), trishula (trident), bhandara-patra (turmeric powder-filled bowl) and khadga (sword). Khandoba's images are often dressed as a Maratha sardar, or a Muslim pathan. Often, Khandoba is depicted as a warrior seated on horseback with one or both of his wives and accompanied with one or more dogs. He is also worshipped as the aniconic linga, the symbol of Shiva. Often in Khandoba temples, both representations of Khandoba — the aniconic linga and the anthropomorphic horseback form.

Legends of Khandoba generally narrate about the battle between the deity and demons Malla and Mani. The principle written source of the legend is Malhari Mahatmya (Mallari Mahatmya), which claims to be from the chapter Kshetra-kanda of the Sanskrit text Brahmanda Purana, but is not included in standard editions of the Purana. R.C. Dhere and Sontheimer suggests that the Sanskrit Mahatmya was composed around 1460–1510 AD, mostly by a Deshastha Brahmin, to whom Khandoba is the family deity. A version is also available in Marathi by Siddhapal Kesasri (1585). Other sources include the later texts of Jayadri Mahatmya and Martanda Vijaya by Gangadhara (1821) and the oral stories of the Vaghyas, bards of the god.

The legend recounts that the demon Malla and his younger brother Mani, who had gained the boon of invincibility from the god Brahma, create chaos on the earth and torment the sages. When the seven sages approach Shiva for protection, Shiva assumes the form (avatar) of Martanda Bhairava (as the Mahatmya calls Khandoba) on Chaitra Shuddha Poornima at Adimailar, Mailapura near Bidar. He rides the Nandi bull, leading an army of the gods. Martanda Bhairava is described as shining like gold and the Sun, covered in turmeric (Haridra), three-eyed and with a crescent moon on his forehead. The demon army is slaughtered by the gods; finally Khandoba kills Malla and Mani. While dying, Mani offers his white horse to Khandoba as an act of repentance and asks for a boon. The boon is that he be present in every shrine of Khandoba, that human-kind is bettered and that he be given an offering of goat flesh. The boon is granted, and thus he transforms a demigod. Malla, when offered a boon, asks for the destruction of the world and human-flesh. Angered by the demon's request, Khandoba decapitates him, and his head falls at the temple stairs where it is trampled by the devotees feet. The legend further describes how two Lingas appeared at Prempuri, the place where the demons were killed.