The River Idle is a river in Nottinghamshire, England. Its source is the confluence of the River Maun and River Meden, near Markham Moor. From there, it flows north through Retford and Bawtry before entering the River Trent at Stockwith near Misterton. The county boundary with South Yorkshire follows the river for a short distance near Bawtry, and the border with Lincolnshire does the same at Idle Stop. Originally, it flowed northwards from Idle Stop to meet the River Don on Hatfield Chase, but was diverted eastwards by drainage engineers in 1628.