Andrew Onderdonk (30 August 1848 – 21 June 1905) was an American construction contractor who worked on several major projects in the West, including the San Francisco seawall in California and the Canadian Pacific Railway in British Columbia.

After starting his career surveying town sites and roads in New Jersey, he headed west to work as a general manager for financier Darius Ogden Mills on several engineering contracts.

When those sections were complete, he continued building eastward under contract with the Canadian Pacific Railway, until he ran out of rail in Eagle Pass in 1885.

From Emory's Bar to Savona, the railway had to be built through the Fraser Canyon, whose immense cliffs required extensive and expensive tunnelling.

At the end of construction, the Chinese labour contracting companies abandoned their charges; thousands of workers were left stranded and living in caves without food and water in the desert heat of the mountains surrounding Spences Bridge.

Generally management considered the Chinese to be efficient, hard-working and well-behaved workers, although many thousands deserted to the goldfields rather than stay in the harsh conditions of the railway camps.

Navigable waters along this entire section of the route enabled supply of construction materials by the steamboats that traveled the Thompson and Shuswap rivers.

In 1899, he tendered a bid for constructing the initial portion of the New York City Subway, but was rejected in favor of John Bart McDonald.

He won the bid to remove the rock and dirt from the tunnel beneath the Hudson River and used the debris to expand Governor's Island.