Granthi is the caretaker of the Guru Granth Sahib, the holy book of Sikhism. He is the person who usually recites the verses from the holy book. The Sikh religion, however, states that any person irrespective of caste, creed or sex can read the verses.
A Granthi is not a priest in the pure sense, since Sikhism does not promote the concept of priesthood. He is appointed in a Gurdwara to maintain order and conduct the daily rites and religious ceremonies. During the last rites of a person the Granthi is summoned to read out the verses from the Guru Granth Sahib, which forms the Antim Ardas.
The first Granthi in Sikh history was Baba Buddha, a revered figure of his times. He was appointed by Guru Arjan Dev to read the verses from the first written copy of the Guru Granth Sahib, which was installed in the Golden Temple of Amritsar.