Highway 104 in Nova Scotia, Canada, runs from Fort Lawrence at the New Brunswick border near Amherst to River Tillard near St. Peter's.

Except for the portion on Cape Breton Island between Port Hawkesbury and St. Peter's, it forms the main route of the Trans-Canada Highway across the province.

In 1970, all sections of Trunk 4 west of New Glasgow were renumbered, although the number was added back in the Mount Thom and Wentworth Valley areas in the 1990s when new alignments of Highway 104 opened to traffic.

From Thomson Station the highway runs southeast for 45 kilometres (28 mi) to Masstown, this segment is a tolled section known as the Cobequid Pass, which opened on 15 November 1997.

[4] Past James River, the highway continues east for 12 kilometres (7 mi) to Addington Forks as a 4-lane divided freeway[4] where the highway runs east for 11 kilometres (7 mi) to South River Road, along a new alignment of 4-lane divided freeway that opened on September 19, 2012.

The highway continues from South River Road as a 4-lane divided freeway, which opened October 22, 2016, for 7 kilometres (4 mi) to Dagger Woods.

Concept designs have shown a new alignment of 4-lane freeway being built around the northwest side of Port Hastings, crossing Highway 105 at a new interchange near an electrical substation.

The new alignment of Highway 104 would proceed east and then southeast approximately following a power line corridor to the Exit 43 interchange in Melville.

From Port Hawkesbury, the highway runs east as a controlled access Super 2 for 34 kilometres (21 mi) to its current eastern terminus at an at-grade intersection with Trunk 4 in River Tillard, near St. Peters.

This designation has also been applied to the remaining Trunk 4 corridor in Cape Breton along the south shore of Bras d'Or Lake from St. Peters to Sydney River.