Coordinates: 56°01′00″N 4°44′00″W / 56.016667°N 4.733333°W / 56.016667; -4.733333

Helensburgh (Baile Eilidh in Gaelic) is a town in Argyll and Bute, Scotland. It lies on the north shore of the Firth of Clyde and the eastern shore of the entrance to the Gareloch.

Helensburgh was formerly in Dumbarton District, but was re-allocated under local government reorganisation in 1996. Prior to 1975 it was part of the former Dunbartonshire.

Helensburgh was founded in 1776 when Sir James Colquhoun of Luss built spa baths on the site of Ardencaple Castle, which dated back to about 1600. He then had the seaside resort town constructed to the east of the spa on a formal layout in the style of Edinburgh New Town, and named it after his wife Helen. A ferry service he arranged across the Firth of Clyde to Greenock was successful in attracting residents who could commute from jobs there to attractive homes in the new town.

In 1808, Henry Bell bought the public baths and hotel, which his wife superintended while he continued his interest in early steamboats such as the nearby Charlotte Dundas and the North River Steamboat which Robert Fulton had just introduced at New York City. To improve hotel trade, he had the paddle steamer Comet constructed and in 1812 introduced Europe's first successful steamboat service, bringing passengers down the River Clyde from Glasgow to Greenock and Helensburgh. The Clyde steamer trade developed rapidly, and Helensburgh pier and Craigendoran pier at the east end of the town both became major departure points. From 1858 holidaymakers were brought to the resort and the steamers by the Glasgow, Dumbarton and Helensburgh Railway terminus built in the centre of the town, and in 1894 a second railway station was opened higher up the hill on the West Highland Railway to Fort William.