Elizabeth Fairburn was born on 29 August 1821 at the Church Missionary Society station at Kerikeri, the daughter of Sarah Tuckwell and her husband, William Thomas Fairburn, a CMS lay missionary. The family moved to Paihia in 1823 to help set up a new mission station; when her parents moved south, Elizabeth stayed on at Marianne Williams's school for missionary daughters.
Growing up in an almost entirely Māori New Zealand, Elizabeth was used to shortages of commodities not easily procured in the country and to limited contact with Europeans. She became skilled in homoeopathic medicine and fluent in the Māori language. As a young woman, at her father's station at Otahuhu, she was known for her ability to teach in Māori. She was the only one of the five Fairburn children to show an inclination for missionary work. When she received a written proposal of marriage from William Colenso, CMS mission printer, she accepted him as a partner in missionary work rather than as the husband of her choice. After a brief and unpromising meeting, they were married at Otahuhu on 27 April 1843, obeying the wishes of Bishop G. A. Selwyn. Colenso was to go to St John's College at Waimate North, to prepare for ordination.
Elizabeth Colenso's competence as a Māori scholar was a compelling reason for Selwyn's wanting her at Waimate where revision of the New Testament in Māori was being carried out. But if she made any contribution, it was not recorded by those associated with this work. She was also put in charge of the new Māori girls' boarding school, a favourite project of the bishop. Her first child, Frances Mary, was born in February 1844 when William was, characteristically, absent on a missionary journey. Both Colensos longed to be settled on a mission station among Māori, and William began to believe that his ordination was being delayed in order to keep Elizabeth at Waimate. However, he was ordained as deacon in September 1844, and at the end of the year the family left to establish the Waitangi mission station at Ahuriri in Hawke's Bay.
Elizabeth Colenso was in an environment not unlike that of her childhood. Māori was the only language spoken, even in the home. She began a school for women and children almost immediately. But there were no other missionary families to give support. When William Colenso fell seriously ill, it was Elizabeth, five months pregnant, who nursed him for eight days and nights. In August 1845, some six weeks before the birth of their second child, Ridley Latimer, the family set out on a journey of 130 miles over rugged country to Poverty Bay where Elizabeth could be under the care of fellow missionary Jane Williams. Apart from this it seems that she never left the mission; whole years passed in which she did not see another European woman. For William there were countless reasons for expeditions; for Elizabeth this meant many weeks of solitary responsibility.
Elizabeth Colenso's journals for this period are lost, but according to William Colenso's account, their marriage had become one of form only. The discovery that William was the father of a child born in 1850 to Ripeka Meretene, a member of the household, was a terrible shock to Elizabeth. For over two years, however, she continued to conduct her school and give loving care to the child, Wiremu, before the situation became generally known. William was suspended from his ministry. While refusing Selwyn's demand that he hand the child over to Māori relatives, he accepted that Elizabeth should take Wiremu with her when she left in August 1853 for Auckland, where their two children were now at school. On her departure she had written to her husband: 'If I had no children I would never leave you.' But away from the isolation of Ahuriri her letters, sympathetic and affectionate, changed in tone and there was a complete severance of ties with William.
Elizabeth Colenso had some private income from land settled on her by her father. However, in 1854 she joined Benjamin Ashwell and his family at the CMS mission at Taupiri in Waikato, to assist with the boarding school for Māori girls. She taught a range of subjects including reading in Māori and English, history, arithmetic and domestic duties. The seven years she spent there, busy and happy, 'greatly strengthened' the work of the school.
In 1861 Elizabeth Colenso took her children to England to continue their education. In London she was soon engaged in philanthropic work with the Church of England. Her interest in a party of Māori, brought to England by William Jenkins, led to her presentation to Queen Victoria. She acted as interpreter, and was also sought as translator by the Colonial Office. Her major work was her contribution to the publication of the first complete Bible in Māori in 1868. The Old Testament, translated over a long period by Archdeacon Robert Maunsell and revised by a committee in New Zealand, was seen through the press by Elizabeth Colenso and the Reverend George Maunsell. It was a lengthy undertaking; she was correcting proofs throughout the mid 1860s, working on the manuscripts of Ecclesiastes, the Song of Solomon, and Isaiah. Returning to New Zealand early in 1867 she helped prepare the revised New Testament for the press, correcting the printed copy, and sometimes suggesting alternative translations. She also wrote scripture stories in Māori.
In 1869 Elizabeth Colenso and her daughter returned to the old mission house at Paihia, where she started a school for Māori children at Te Tii, near the mouth of the Waitangi River. Invited to join the Melanesian mission at Norfolk Island, she taught there from 1876 to 1898, and translated works into Mota, the mission's common language. Crippled with rheumatism, though still translating, she retired to live with her daughter, Frances Mary Simcox, and her family at Forest Lakes, Otaki, where she died on 2 September 1904.
Elizabeth Colenso was 'sincere, humble, unselfish and generous'. Although she had remarkable talent, her commitment to teaching in mission schools kept her in a subordinate role. While her skill with written Māori was outstanding, the choice to spend the latter part of her life with the Melanesian mission suggests that her primary impulse was an evangelising one.