Barna da Siena, also known as Berna di Siena, was a Sienese painter active from about 1330 to 1350, and was the painter in Siena during this period. He learned his trade from Simone Martini. Barna is believed to have paint the frescoes depicting the life of Jesus in the Collegiata di San Gimignano and is generally credited with Christ Bearing the Cross, with a Dominican Friar in the Frick Collection in New York City. He was killed in a fall from the scaffolding. Barna's figures are more dramatic and vigorous than any in previous Sienese painting.

There is a vast amount of debate and uncertainty over who Barna da Siena was. Because of a lack of signed works Barna is credited as the master of the Collegiata di San Gimignano. It is believed that his pupil Giovanni d' Asciano assisted him on the frescoes and finished the left-over portions after Barna reportedly fell from a scaffolding and died supposedly at a young age. It is suggested, based on the works of biographer Giorgio Vasari, that the master working in the Collegiata di San Gimignano was named Bernardo Bertini. Bernardo was notably taken prisoner in 1335 during a skirmish with the Luccans. He later went to Siena and studied in Simone Martini's workshop. Documents show that in 1355 he was either absent from Siena or dead. This supports the notion that Barna, the master of San Gimignano, died fairly young. Somewhere around 1360. When captured in 1335 it was noted that he was just a lad. If he was born shortly before 1320 and died somewhere before 1360 then he could not have been older than forty before his death.