Mechanics Bay (Māori: Te Tōangaroa) is a reclaimed bay on the Waitematā Harbour in Auckland, New Zealand. It is also the name of the area of the former bay that is now mainly occupied by commercial and port facilities. Sometimes the bay formed between Tāmaki Drive and the western reclamation edge of Fergusson Container Terminal is also referred to as Mechanics Bay.^{[citation needed]}

The bay was called Te Tōangaroa by Tāmaki Māori, referring to the need to drag waka a long distance during low tide in the bay. During the early colonial era of Auckland, Mechanics Bay was the main trading port on the Waitematā Harbour for Māori, in a separate location from the main Auckland waterfront.

Along the harbour shore between Point Britomart and St Stephen's Point in Parnell were four bays: Official Bay, Mechanics Bay, St Georges Bay and Judges Bay. Some have now disappeared due to land reclamation and the quarrying of the bordering headlands. Closest to Point Britomart was Official Bay, so called because many government officials lived there during the 1840s.

Almost contiguous with Official Bay was Mechanics Bay. It took its name from its use in housing the labour force the government had brought to construct the new capital. Mechanics Bay contained the mouth of the stream issuing from the springs in the Auckland Domain to the south. The Bay had a broad, flat beach where Māori had long been in the habit of beaching their waka (canoes).

Next to Mechanics Bay was St George's Bay and then Judges Bay, so named because three of the magistrates of the early colony built their houses there. Next to Judges Bay is St Stephen's point, where a small chapel was built.

As early as the 1860s this shore front began to be modified by the European settlers. In particular it was in order to get the railway tracks around to the bottom of Queen Street that Point Britomart was quarried away and Official Bay and Mechanics Bay filled in. Initially the railway tracks came through the gully that lay between the Auckland Domain and the suburb of Parnell, but later when a second route was formed further to the east through Meadowbank the shoreline between Mechanics Bay and Hobson Bay was also modified. St Georges Bay ceased to exist and became the shunting yard for the railway station, and Judges Bay was separated from the harbour by a railway embankment.

The major thoroughfare of Mechanics Bay is Beach Road, which once ran around the beach front of the now reclaimed Mechanics Bay. The former Auckland Railway Station is located here, an impressive brick 1930s structure designed by Gummer and Ford. Formerly located at the bottom of Queen Street, the station was moved to Beach Road to be the centrepiece for the new downtown business area of Auckland. The plan was not a success. The station was decommissioned and the railway terminal returned to its original location, now named the Britomart Transport Centre.

New Zealand's first international airport was in Mechanics Bay. The first aircraft connecting New Zealand with the rest of the world in the 1930s were flying boats. International flights from Britain by Imperial Airways via India, Singapore and Australia connected with TEAL for the Sydney to Auckland leg. Flights by Pan American from America via Hawaii also landed at Auckland. The Short Solent or Boeing 314 flying boats landed in Mechanics Bay, which was the centre of international aviation for New Zealand until the 1950s. Even after the construction of Auckland International Airport at Māngere in the 1960s, Mechanics Bay was still used by flying boats to the Pacific Islands, e.g. for the Coral Route to Fiji.