The first papal conclave held in the Sistine Chapel took place in 1492.
A papal conclave is the closed election in which cardinals choose a new pope. The Sistine Chapel became the setting for this process after it had been completed and decorated for papal worship and ceremony. The 1492 conclave elected Cardinal Rodrigo Borgia, who took the name Pope Alexander VI.
This election occurred before Michelangelo painted the ceiling. At that time, the chapel already had important fifteenth-century frescoes by artists including Perugino, Botticelli, and Ghirlandaio, but its later Renaissance appearance was not yet complete.
The chapel is now strongly associated with conclaves, although the election of a pope has not always taken place there. The 1492 vote is significant because it marks the first conclave specifically held in the Sistine Chapel, rather than merely identifying the chapel with the ceremony in general.