Mahamandaleshwar (or Maha Mandaleshwar) is a title used by some Hindu monks of the Dashanami order of renunciates ("swamis") founded by Shankaracharya. A person called Mahamandaleshwar has been elevated by his peers to the highest level of traditional, Hindu spiritual guardianship. Today India has 530 Mahamandaleshwars who carry on the work begun by Adi Shankarachara circa 2500 years ago.
Literally, "Mahamandaleshwar" means "Superior of great and/or numerous monasteries" or "Superior of a religious district or province" (maha = great, mandala = district, ishwara = head, sovereign). There are two systems of organization in the dashanami order. Each of the ten names (dasha = ten, nami = name), which is appended to a monk's given name at initiation, is assigned to one of the four cardinal monastic seats founded by Shankaracharya and presided over by his direct successors at Joshimath in North India, Dwarka in the West, Shringeri in the South and Puri in the East.
The other system is the akhara system of which the Mahamandaleshwaras are a part. Their origin dates from the early days of Islamic invasions into India (around or just prior to 1000 CE) when many monks became the targets of murderous attacks. In order to protect themselves, they formed "regiments" of monk-warriors who, to this day, preserve the traditional martial arts of India in addition to their spiritual practices. So in addition to being a way to organize the orders at a local level they have historically also served as paramilitary regiments with the Mahamandaleshwaras as generals, as it were, of these regiments.
As of now, Shri Ashutoshgiri Goswami (who is also Mahant of Bhimnath Mahadev, Gujarat) is Mahamandaleshwar crowned by Swami Avdeshanandji at the pious (and Equally Popular) Kumbha Mela. At the same time, Swami Avdeshanandji announced Bhimnath Mahadev as a "Pith" and Mahant of Bhimnath will also be called as "Pithadheesh".