Palm Sunday is a Christian moveable feast that falls on the Sunday before Easter. The feast commemorates Jesus' triumphal entry into Jerusalem, an event mentioned in all four canonical Gospels. (Mark 11:1–11, Matthew 21:1–11, Luke 19:28–44, and John 12:12–19).

In many Christian churches, Palm Sunday is marked by the distribution of palm leaves (often tied into crosses) to the assembled worshipers. The difficulty of procuring palms for that day's ceremonies in unfavorable climates for palms led to the substitution of boughs of box, yew, willow, olive, or other native trees. The Sunday was often designated by the names of these trees, as Yew Sunday, or by the general term Branch Sunday.

In the accounts of the four canonical Gospels, Jesus' triumphal entry into Jerusalem takes place about a week before his Resurrection.

According to the Gospels, Jesus rode a donkey into Jerusalem, and the celebrating people there lay down their cloaks in front of him, and also lay down small branches of trees. The people sang part of Psalms 118: 25–26 – ... Blessed is He who comes in the name of the Lord. We bless you from the house of the Lord ....

Sunday (ⁱ/ˈsʌndeɪ/ or /ˈsʌndi/) is the day of the week between Saturday and Monday. For most Christians, Sunday is observed as a day for worship of God and rest, due to the belief that it is Lord's Day, the day of Christ's resurrection.

Sunday is a day of rest in most Western countries, part of 'the weekend'. In most Muslim countries, and Israel, Sunday is a working day.

According to the Hebrew calendars, traditional Christian calendars, Sunday is literally the "first day" of the week. According to the International Organization for Standardization ISO 8601 Sunday is the seventh and last day of the week.

No century in the Gregorian calendar starts on a Sunday, whether its first year is '00 or '01. The Jewish New Year never falls on a Sunday. (The rules of the Hebrew calendar are designed such that the first day of Rosh Hashanah will never occur on the first, fourth, or sixth day of the Jewish week; i.e., Sunday, Wednesday, or Friday).

The English noun Sunday derived sometime before 1250 from sunedai, which itself developed from Old English (before 700) Sunnandæg (literally meaning "sun's day"), which is cognate to other Germanic languages, including Old Frisian sunnandei, Old Saxon sunnundag, Middle Dutch sonnendach (modern Dutch zondag), Old High German sunnun tag (modern German Sonntag), and Old Norse sunnudagr (Danish and Norwegian søndag, Icelandic sunnudagur and Swedish söndag). The Germanic term is a Germanic interpretation of Latin dies solis ("day of the sun"), which is a translation of the Ancient Greek heméra helíou. The p-Celtic Welsh language also translates the Latin "day of the sun" as dydd Sul.