Mariano Juaristi Mendizábal (February 21, 1904 – January 12, 2001) was a Spanish Basque pelota player known as Atano III.

Mariano Mendizábal was born on 1904 in Azkoitia, Guipúzcoa, Spain in the Caserío Atano from which his family pseudonym comes.

[2] Mendizábal's winning streak started in 1926 when he beat the best player of the time and champion, Juan Bautista Azcárate.

During the title dispute, played in a series of three games, Mendizábal beat his rival with the final scores of 22-19, 22-12 and 22-9.

[7] After his retirement, in 1967 received the deportive merith medal and the main fronton of San Sebastián was renamed from Anoeta to Atano III after him.