Henry Grattan Guinness (11 August 1835 – 21 June 1910) was an Irish Nonconformist Protestant preacher, evangelist and author.

His father was John Grattan Guinness (1783–1850), Arthur's youngest son, who was an officer in the Madras Army of the East India Company.

In the evening it amounted to 1600, and if there were a place large enough, five times the number would have been present, to hear this highly gifted preacher.

Judges, members of Parliament, orators, Fellows of College, lights of the various professions, the rank and fashion of the metropolis have been drawn out.

[citation needed] Fanny was a partner in the missionary work and she was not only responsible for the administration, but she would also preach to audiences of men and women.

In September 1866 while in Keighley, Yorkshire, Guinness saw a notice advertising a series of lectures by the freethinker and communist Harriet Law.

[2] With the help of Professor John Couch Adams, some astronomical tables and examination of the scriptures, Guinness worked out the prophetic chronology of the bible in terms of a series of "solilunar cycles.

"[5] This proved to him that he was living at the end of the sixth unsabbatic day of creation, 6,000 years from Adam, and that the "redemption Sabbath" would soon arrive.

In 1873 Guinness founded the East London Institute for Home and Foreign Missions, the root of the Regions Beyond Missionary Union.

His son Dr. Henry Grattan Guinness (1861–1915), known as Harry to distinguish him from his father, founded the Congo-Balolo Mission in 1888 and co-founded the Congo Reform Association in 1904.

Dr. Gershom Whitfield Guinness was a medical missionary to China who escaped the Boxer Rebellion and went on to found the first hospital in Henan south of the Yellow River.

A granddaughter, Ruth Eileen, married the famous geneticist and statistician Ronald Fisher, one of those responsible for Neo-Darwinism.

His daughter Lucy wrote Across India at the Dawn of the 20th Century, about her hopes of converting the heathen natives to Christianity.