Atto of Pistoia was a Benedictine monk and Catholic bishop who lived from approximately 1070 to 1153. Born in Tuscany, though possibly in Beja or Badajoz, he rose through the ranks of the Vallombrosan order, serving as abbot of Vallombrosa in 1105 and later as abbot-general around 1120. He eventually became the Bishop of Pistoia in 1135. Beyond his ecclesiastical duties, he was a recognized historian who wrote biographies of figures such as John Gualbert and Bernard degli Uberti.