She was born and brought up as a Methodist in Gortmore, near Omagh, County Tyrone. Milligan's father was the writer Seaton Milligan, antiquary and member of the RIA. Alice was one of eleven children, including music collector Charlotte Milligan Fox, and from 1877 to 1887 attended Methodist College, Belfast, after which she completed a teacher-training course. Together with her father she wrote a political travelogue of the north of Ireland in 1888, Glimpses of Erin. She wrote her first novel, A Royal Democrat, in 1890.
After the death of Parnell she became an ardent nationalist. In 1894 with Jenny Armour she founded branches of the Irish Women's Association in Belfast and other places, and became its first president. With Ethna Carbery she founded two nationalist publications in the 1890s, The Northern Patriot, and later The Shan Van Vocht, a monthly literary magazine published in Belfast from 1896 to 1899.
She was a figure of the Irish literary revival, and a close associate of Douglas Hyde. She was also 'on first-name terms' with WB Yeats, James Connolly and Roger Casement. Tomas MacDonagh, writing in the Irish Review in September 1914, described her as 'the best Irish poet of his generation'.
During 2010/2011 Ulster History Circle mounted plaques for famous Ulster figures. Charlotte Milligan Fox and Alice Milligan have a plaque mounted on Omagh Library, 1 Spillar's Place, Omagh, Co Tyrone.
- Glimpses of Erin (with Seaton Milligan, London, 1888)
- A Royal Democrat (London, 1890, as Iris Olkyrn)
- Life of Theobald Wolfe Tone (Belfast, 1898)
- Hero Lays (Dublin, 1908)
- Oisín in Tír-nan-Óg. Translated by Tadhg Ó Donnchadha (1909)
- Sons of the Sea Kings (with William Milligan, Dublin, 1914)
- Two Poems of Triumph in Death (with Alice Furlong, Dublin, 1917)
- The Dynamite Drummer (with William Milligan, Dublin, 1918)
- We Sang for Ireland: Poems of Ethna Carbery, Seumas MacManus, Alice Milligan (1950) (1950)
- Poems (1954)
- Harper of the Only God: Selected poems by Alice Milligan (1993), edited by Sheila Turner Johnston
- Ulster History Circle - The Milligan Sisters: Promoters of the Celtic Revival Archived 2013-10-25 at the Wayback Machine. Accessed 2 September 2014
- Gonzalez, Alexander. Irish Women Writers: An A-Z Guide, p. 219
- RIA Dictionary of National Biography, 2009
- McClements, Freya (18 November 2010). "Omagh's hidden cultural 'heroine'". BBC. Retrieved 19 November 2010.
- Ulster History Circle. "Ulster History Circle Annual Report 2010-2011" (PDF). Retrieved 2019-01-23.
- Johnston, Sheila (1994). Alice: A Life of Alice Milligan. Colourpoint Books. ISBN 978-1-898392-01-9.
- Morris, Catherine (2012). Alice Milligan and the Irish Cultural Revival. Dublin: Four Courts Press. ISBN 978-1-84682-313-8. Archived from the original on 2013-02-17.
- Harp, Richard (Spring 2000). "No Other Place But Ireland: Alice Milligan's Diaries and Letters". New Hibernia Review. 4 (1): 79–87.