Ọ̀ṣun Òṣogbo is a fourteen-day festival held in August of each year. It culminates in a massive procession to the Ọ̀ṣun Grove where rituals with the sacred objects carried by the Arugbá (votary maid) to the main Ọ̀ṣun Shrine are conducted.
Priests and Priestesses are wearing white robes, in honour of Ọ̀ṣun, the òrìṣà (deity) of fertility and they plait their hair in the traditional way of olórìṣà (one who is initiated in a Yorùbá divinity). The bell they use when offering prayers to Ọ̀ṣun is called ààjà and the sound of it serves to draw the attention of the goddess.
Traditionalists believe that the Ọ̀ṣun river water is sacred and that the òrìṣà helps those who take her water, called àgbo by devotees. People come with containers to carry home the water from the Ọ̀ṣun river which is believed to also have healing properties.
The Ọ̀ṣun Festival in the Groves had dwindled in size to only a very small number of traditionalists prior to the arrival of Susanne Wenger in the late 1950s and the subsequent revitalization of the shrines by the New Sacred Art Movement, which Wenger founded. In the decades since, the festival has grown to become the largest and most important festival in Yorùbáland, if not in the whole of Nigeria. The numbers are not formally recorded but it is said that tens of thousands of people join in the procession each year.
Hundreds of devotees make the pilgrimage yearly from foreign countries. Many of these come from South America and the Caribbean where Yorùbá religious traditions were passed down to the descendants of slaves taken from Yorùbáland, including Brazil, Cuba, and Trinidad and Tobago. African Americans also come to Nigeria, and particularly Òṣogbo in increasing numbers, as interest in their African heritage and traditions grows.