The 2006 Ontario terrorism case was the plotting of a series of attacks against targets in Southern Ontario, Canada, and the June 2, 2006 counter-terrorism raids in and around the Greater Toronto Area that resulted in the arrest of 14 adults and 4 youths (the "Toronto 18"). These individuals have been characterized as having been inspired by al-Qaeda.

They were accused of planning to detonate truck bombs, to open fire in a crowded area, and to storm the Canadian Broadcasting Centre, the Parliament of Canada building, the Canadian Security Intelligence Service (CSIS) headquarters, and the parliamentary Peace Tower to take hostages and to behead the Prime Minister and other leaders.

Following the jury trial in June 2010, a comprehensive presentation of the case and the evidence obtained from court exhibits previously restricted was given by Isabel Teotonio of the Toronto Star. It contained the details on guilty pleas, convictions, and stayed/dismissed charges. The Ontario Court of Appeal released their decision on December 17, 2010.

Seven adults pleaded guilty, including the two ringleaders—Fahim Ahmad, who was sentenced to 16 years, and Zakaria Amara, who received a life sentence and initially had his Canadian citizenship revoked but later restored following the passage of Bill C-6. The remaining five received sentences ranging from seven to 20 years. A further three adults and one youth were convicted at trial; the youth was sentenced to 2.5 years while the adults received sentences of 6.5 years, ten years, and life imprisonment. Four adults and two youths were released after the charges against them were stayed and one youth had his charges dismissed.

On November 27, 2005, Mubin Shaikh (a police agent) met with members of the terrorist group at an information meeting at a banquet hall regarding the use of security certificates in Canada, and began his infiltration of the group. He was told that they had planned a training camp near Orillia. They asked Shaikh if he would join them and teach them how to use a gun, since he had mentioned his military and martial arts training, and shown them his Possession and Acquisition Licence.

The trip by the group, ages 15–42, was to a wooded area near Orillia, Ontario, from December 18–31, 2005. It was monitored by more than 200 police officers.

Authorities say that "the internet played a large role in the suspects' planning". Six months prior to the planned attack, the group watched a video over the internet of Anwar al Awlaki (the imam who was connected to three of the 9/11 hijackers) preaching about the need for jihad.

The ringleader gave sermons comparing the Canadian countryside to Chechnya, and calling for victory over "Rome", which prosecutors alleged was a reference to Canada. "Whether we get arrested, killed, or tortured, our mission is greater than just individuals," he said. He also said: "We're not officially al-Qaida but we share their principles and methods" around a campfire.