The Birrega Main Drain is a drainage canal in the southern suburbs of Perth, Western Australia.

The canal stretches from Darling Down, where it starts just west of the South Western Highway, to Baldivis, where it discharges into the Serpentine River.

[4][5] The drain was not constructed for flood protection but rather to dewater its drainage area to make it suitable for agriculture by alleviating water logging in winter.

[1][2] The drain changes from its westerly direction to a southerly in Oakford and reaches a width of 40 metres at Mundijong Road, where it enters Baldivis and the City of Rockingham.

[1][2] The upper reaches of the drain, in Hilbert, where scheduled to be revegetated as part of the construction of The Avenues housing estate, being advertised as the Birrega Living Stream.