The Witham Navigable Drains are located in Lincolnshire, England, and are part of a much larger drainage system managed by the Witham Fourth District Internal Drainage Board. The Witham Fourth District comprises the East Fen and West Fen, to the north of Boston, which together cover an area of . In total there are over of drainage ditches, of which under are navigable. Navigation is normally only possible in the summer months, as the drains are maintained at a lower level in winter, and are subject to sudden changes in level as a result of their primary drainage function, which can leave boats stranded. Access to the drains is from the River Witham at Anton's Gowt Lock.