king's highway 17, more commonly known as highway 17, is a provincially maintained highway and the primary route of the trans-canada highway through the canadian province of ontario. it begins at the manitoba boundary, west of kenora, and the main section ends where highway 417 begins just west of arnprior. a small disconnected signed section of the highway still remains within the ottawa region between county road 29 and grants side rd. this makes it ontario's longest highway.