The Helena River is a tributary of the Swan River in Western Australia. The river rises in country east of Mount Dale and flows north-west to Mundaring Weir, where it is dammed. It then flows west until it reaches the Darling Scarp. It passes through the western edge of the Darling Scarp between Gooseberry Hill, and Greenmount Hill before joining the Swan River at the southern edge of the historic town, now suburb, of Guildford.