The Battle of Ridgeway (sometimes the Battle of Lime Ridge or Limestone Ridge) was fought in the vicinity of the town of Fort Erie across the Niagara River from Buffalo, New York, near the village of Ridgeway, Canada West, currently Ontario, Canada, on June 2, 1866, between Canadian troops and an irregular army of Irish-American invaders, the Fenians. It was the largest engagement of the Fenian Raids, the first modern industrial-era battle to be fought by Canadians and the first to be fought only by Canadian troops and led exclusively by Canadian officers. The battlefield was designated a National Historic Site of Canada in 1921 and is the last battle fought within the current boundaries of Ontario against a foreign invasion. The action at Ridgeway has the distinction of being the only armed victory for the cause of Irish independence between the Irish Rebellion of 1798 and the Easter Rising in 1916.

The Fenian Brotherhood (Irish: Bráithreachas na bhFíníní) was an Irish republican organisation founded in the United States in 1858 by John O'Mahony and Michael Doheny. It was a precursor to Clan na Gael, a sister organisation to the Irish Republican Brotherhood. Members were commonly known as "Fenians". O'Mahony, who was a Gaelic scholar, named his organisation after the Fianna, the legendary band of Irish warriors led by Fionn mac Cumhaill.