Josua Mateinaniu was a preacher and catechist (teacher) in the Methodist Church of Fiji and Rotuma. A wanderer and a sailor at first, he drifted in his travels to Tonga, where he became a Christian.
In 1835, Mateinaniu helped William Cross and David Cargill in their linguistic preparations for the mission to Fiji. He became a preacher and came back to his own land with Cross and Cargill, and was himself a most important factor in the missionary impact made on Lakeba from the start. He went ahead of the first missionaries to Somosomo, and preached there with some success among the Tongans, who were in the service of Tui Cakau at that time, thus making it possible for Hunt and Lyth, to establish that station.
Of Mateinaniu, Cargill wrote the following in his wife, Margaret's memoirs:
He preached in Bau regularly, long before it was really opened to white missionaries. At the time of Hunt's death, he was stationed at Viwa; he and his wife personally cared for Hunt's family during the long weeks of that final illness.
One of the four houses at Lelean Memorial School, a Methodist church secondary school located at Davuilevu, Nausori, is named in honour of Mateinaniu.