The ancient Persians painted eggs for Nowrooz, their New Year celebration, which falls on the Spring equinox. The Nawrooz tradition has existed for at least 2,500 years. The decorated eggs are one of the core items to be placed on the Haft Seen, the Persian New Year display. The sculptures on the walls of Persepolis show people carrying eggs for Nowrooz to the king.
At the Jewish Passover Seder, a hard-boiled egg dipped in salt water symbolizes the festival sacrifice offered at the Temple in Jerusalem.
The pre-Christian Saxons had a spring goddess called Eostre, whose feast was held on the Vernal Equinox, around 21 March. Her animal was the spring hare. Some believe that Ēostre was associated with eggs and hares, and the rebirth of the land in spring was symbolised by the egg. Ēostre is known from the writings of Bede Venerabilis, a seventh-century Benedictine monk. Bede describes the pagan worship of Ēostre among the Anglo-Saxons as having died out before he wrote about it. Bede's De temporum ratione attributes her name to the festival, but does not mention eggs at all.
Other theories such as Jakob Grimm’s in the 18th Century believe in a pagan connection to Easter eggs via a putatively Germanic goddess called Ostara.
Pope Gregory the Great ordered his missionaries to use old religious sites and festivals, and absorb them into Christian rituals where possible. The Christian celebration of the Resurrection of Christ was ideally suited to be merged with the Pagan feast of Eostre, and many of the traditions were adopted into the Christian festivities. There are also good grounds for the association between hares (later termed Easter bunnies) and eggs, through folklore confusion between hares' forms (where they raise their young) and plovers' nests.
And as a bonus: The English name for the festival of Easter derives from the Germanic word Eostre. It is only in Germanic languages that a derivation of Eostre marks the holiday. Most European languages use a term derived from the Hebrew pasch meaning Passover. In Spanish, for example, it is Pascua; in French, Pâques; in Dutch, Pasen; in Greek, Russian and the languages of most Eastern Orthodox countries: Pascha. In Middle English, the word was pasche, which is preserved in modern dialect words. Some languages use a term meaning Resurrection, such as Serbian Uskrs.