The Mortlake Pipeline is a transmission pipeline located in western Victoria. The pipeline is owned by the SEA Gas (Mortlake) Partnership, which is jointly owned by the APA Group (50 per cent) and REST (Retail Employees Superannuation Trust) (50 per cent), an industry superannuation fund.

The pipeline is 83 km in length and has a diameter of 508mm and a capacity of 400 TJ/day. It provides gas from the SEA Gas Pipeline to the 550MW open cycle gas turbines at Mortlake Power Station. Gas is stored at the power station before supplying the Victorian market via the Victorian Transmission System (VTS).

The Mortlake Pipeline is currently a non-scheme pipeline, and is subject to the access regime for non-scheme pipelines under Part 10 of the National Gas Rules (NGR). It was previously subject to the access regime for non-scheme pipelines under the former Part 23 of the NGR, which was replaced by Part 10.

The AER has granted the following exemptions for the Mortlake Pipeline:

• On 3 January 2018, a five year category 2 exemption under Part 23 of the NGR.
• On 30 November 2022, a five year Category 2 exemption under Part 23 of the NGR. Due to reforms to the NGR, the exemption transitioned to a Category 2 exemption under Part 10 of the NGR.

The Mortlake Pipeline was commissioned in January 2011. It was initially owned by Origin Energy, but was sold to the SEA Gas (Mortlake) Partnership in 2016.