The Anglican Diocese on the Niger is the mother diocese (oldest diocese) of the Church of Nigeria (Anglican Communion). It is one of 10 Anglican dioceses in the Anglican Province of the Niger within the Church of Nigeria. The diocese was created in 1864 as the Diocese of Western Equatorial Africa. In 1920 the Diocese of Equatorial West Africa was divided into two: an eastern part (the continuing Diocese, now named the Diocese on the Niger) and a western part (a new Diocese, named the Diocese of Lagos). A part of the Diocese on the Niger was subsequently carved out in 1946 to create the Niger Delta Diocese.
Originally part of Province Two of the Church of Nigeria when the church was divided into three provinces in 1997, Diocese on the Niger became a diocese in the Province of Niger when the Church was reorganised in 2002.
The cathedral church of the diocese is the Cathedral Church of All Saints, Ozala, Onitsha. Started in 1949, the completed cathedral was dedicated for worship on 1 November 1992.