Martin was born at Ross House in Connemara, County Galway, the youngest of sixteen children of James Martin of Ross (1804–1872). The Martin family, a branch of the Martyn family - one of the Tribes of Galway - had settled at Ross by the early 17th century, having previously inhabited the town of Galway for some three hundred years. Her father, James, was a Protestant, his grandfather having converted from the Catholic faith in order to retain the family estates under the Penal Laws. She was a kinswoman of Richard Martin ("Humanity Dick") and her contemporary, Edward Martyn, two other notable members of the Tribe. Her older brother, Robert, was a noted songwriter and a well-regarded member of the Tory party in London.
Her father had managed to save both his estate and his tenants during the Famine - boasting that not one of his people died during the disaster - but at the cost of bankruptcy. Following his death in 1872, the family moved to Dublin and only returned to Ross in 1888.
Violet Martin and Edith Somerville were second cousins, and originally met on January 17, 1886 at Castletownshend, after which they became lifelong companions and literary partners. They came to share a home in Drishane, County Cork. In 1889, Violet adopted the pseudonym Martin Ross, which comprised her surname and the name of her ancestral home; thus the authors were called Somerville and Ross. Their works include The Real Charlotte (1889), Some Reminisences of an Irish R.M. and In The Vine Country.
Violet was seriously injured in a horse-riding accident in 1899, from which she never fully recovered. This was a contributing factor to her death in Drishane, County Cork, in 1915. Edith Somerville continued to write under their joint literary names, claiming that they were still in contact.
The two women left thousands of letters and 116 volumes of diaries, detailing their lives, much of them yet unpublished.