Sham Ennessim (Arabic: شم النسيم, Sham Al Nassim or Sham an-Nassim; Egyptian Arabic: Sham Ennesim, IPA: [ˈʃæmm ennɪˈsiːm]) is a festival marking the beginning of spring, celebrated by Egyptians of all religions. It is an official public holiday in Egypt. Sham Ennessim always falls on Easter Monday, which is the day after Easter, in accordance with the Coptic Orthodox Church. The Arabic name Sham Ennesim translates into "Smelling/Taking In the Zephyrs".

The festival is characterized by a number of traditional practices. Egyptians typically spend the entire day outdoors, engaging in picnics in public gardens, green spaces, along the Nile, or at the zoo. The customary foods consumed on this occasion include fesikh, a fermented, salted, and dried grey mullet, along with lettuce, green onions, and lupin beans. A widespread tradition associated with the festival is the coloring of boiled eggs, which are subsequently eaten or exchanged as gifts.

The exact origin of the festival remains insufficiently documented; however, it is generally held that Sham Ennessim traces back to ancient Egypt. It has been proposed that the modern name is derived from the harvest season, Šmw (Shemu), and that the festival itself is a continuation of early forms of springtime festivities dating back over 4,500 years.

The arrival of spring was considered a time of profound importance for the ancient Egyptians, as it signaled the beginning of the agricultural cycle, an essential phase for sowing, cultivation, and eventual harvest. The seasonal shift held deep symbolic and practical significance in the rhythms of Egyptian life.

Throughout medieval Egypt, Sham Ennessim remained widely observed, persisting across successive regimes including the Fatimids, Ayyubids, and Mamluks. The festival retained a largely non-religious character, maintained instead through its integration into local custom and seasonal rhythms. Its position in the calendar reflects the continuity of earlier seasonal rites that predate both Christianity and Islam in Egypt. Participation extended across religious lines, with Muslims, Christians, and Jews in Egypt marking the day through shared customs.

The Fatimids in particular paid special attention to Sham Ennessim, allowing it to flourish as a public festival while incorporating aspects of it into official state ceremonial life. Although the celebration was rooted in pre-Islamic traditions, the Fatimid regime did not suppress its observance. Instead, it permitted the continuation of established customs and at times adopted a participatory role in their public expression.

Notably, the Fatimid state organized formal celebrations of Sham Ennessim. These included an official procession led by the caliph and accompanied by high-ranking state officials. The event was coordinated by the court preacher, assisted by a cadre of appointed captains, and proceeded through the streets of Cairo as part of a large public spectacle.

Foods such as fesikh, green onions, lettuce, eggs and malana (chickpeas) remained central to the celebration. A tradition persisted during medieval Egypt of writing wishes on eggshells and hanging them from trees, a practice likely derived from earlier symbolic uses of the egg in ritual contexts. It was believed that as the sun rose and its rays touched the eggs, the wishes written upon them would manifest. Women would also make necklaces of lotus flowers to give to their husbands.