The Shiners' Wars were violent outbreaks in Bytown (now Ottawa) from 1835 to 1845 between Irish-Catholic immigrants, led by Peter Aylen, and French Canadians, led by Joseph Montferrand.

The war began when Aylen, a major Irish timber operator, organized a group of Irishmen to attack other timber operations—this group was known as the "Shiners." The Shiners attacked French-Canadian timber rafts and the town's political institutions, as well as brawling with French Canadians on the streets.

In an attempt to control the violence, the citizens of Bytown created the Association of the Preservation of the Public Peace in Bytown, which included armed patrols; however, the violence continued. In the spring of 1837, the violence was brought under control after the government deployed troops to arrest the Shiners. Occasional violence still occurred until 1845 by groups claiming to be the Shiners.

In 1832, the Rideau Canal had just been constructed. Its completion left many Irishmen out of work. To add to the unemployment, the lumber industry was dominated by French Canadians. At the time, they considered the Irish to be at the lowest rung of the social ladder due to historical antipathy and their refusal to assimilate. Many Irish lumbermen were laid off and moved to the Bytown area (now Ottawa Valley), where they displaced some of the area's French timber workers.

Peter Aylen, a major Irish timber operator, was sympathetic to the Irishmen, gaining him their allegiance. He organized a gang of Irish supporters—calling them the "Shiners"—to attack other timber operations. Aylen personally gained an advantage from this violence (which was primarily in the form of brawling) as it disrupted his competitors.

The Shiners were accused of such crimes as assault, arson, rape, and murder. On one occasion, the pregnant wife of a farmer, who had upset the Shiners somehow, was attacked while driving home in a sleigh with other female family members. Beaten with sticks, the farmer's wife attempted to jump to safety, but her clothing got caught in the sleigh and she was dragged over the frozen ground before coming free. The Shiners cut her horses loose from the sleigh, running them off. The horses managed to find their way home the next day; their ears and tails had been mutilated. Other actions also attributed to the Shiners' campaign of terror included stripping children naked in the snow, polluting wells, accosting women in the street, and shattering windows. On one occasion, they reportedly broke up a funeral procession and threw the coffin off of the hearse into the street.

In 1835, Shiners began interdicting timber rafts owned by French Canadians going down the Ottawa River to Montreal.

As well as gaining control of the lumber industry, Aylen set his sights to taking over Bytown. Aylen ordered his Irish supporters to attack French Canadian and drive them out of the area, thus guaranteeing jobs and high wages to the Irish, especially the Shiners. Though special constables were assigned as peacekeepers, they were on Aylen's payroll or for some other reason looked the other way. When pursued, all that the hooligans had to do to evade arrest was cross the border into Lower Canada. As there was no jail or courthouse in Bytown, those who were arrested had to be transported to Perth, Ontario, for trial. However, poorly-paid officers were reluctant to make the 50-mile trip, fearing being ambushed along the way.