Darley is a residential suburb immediately north of and adjoining Bacchus Marsh. It is 50 km west of Melbourne. The name is thought to have been inspired by Darley in Derbyshire, England.

Darley is on the Lerderderg River and a quarry was operated in the 1860s near where the river is joined by Goodmans Creek. In addition to freestone from the quarry, a firebrick factory was opened in the 1880s (later Darley Refractories in Grey Street).

During World War II an Army training camp accommodating 4000 servicepersonnel was built at Darley. A military camp plaque is in Camerons Road.

Darley is separated from Bacchus Marsh by the Western Freeway. It has the Darley Plaza shopping centre (1990, supermarket and eight shops), Darley primary school (1981), Pentland primary school (1993) and the Darley Park recreation reserve. The Bacchus Marsh golf course adjoins the Lerderderg River further north. There are extensive neighbourhood parks in the newer residential area near the golf club. Its primary school enrolment in 2014 was 586 and Pentland’s school enrolment was 169.

Darley's census populations have been:

Census Date Population
1861 29
1890 120
1947 278
2006 6754
2011 7418