Pentecost (lang-grc?????????? polytonic?????, Pent?kost? h?mera, "the Fiftieth day") is one of the prominent feasts in the Christian liturgical year commemorating the descent of the Holy Spirit upon the disciples (Disciple (Christianity)) of Christ. The feast is also called Whitsun, Whitsunday, Whit Sunday, or Whitsuntide, especially in the United Kingdom. Pentecost is celebrated seven weeks (50 days) after Easter Sunday, hence its name. Pentecost falls on the tenth day after Ascension Thursday.

Pentecost is historically and symbolically related to the Jewish harvest festival of Shavuot, which commemorates God giving the Ten Commandments at Mount Sinai fifty days after the Exodus (The Exodus). Among Christians, Pentecost commemorates the descent of the Holy Spirit upon the Apostles (Twelve apostles) and other followers of Jesus as described in the New Testament Acts of the Apostles 2:1-31 . For this reason, Pentecost is sometimes described as the "Birthday of the Church".

The Pentecostal movement of Christianity derives its name from this biblical event.