Lachlan may refer to:

People

• Lachlan (name), masculine name.

Places

• Several places in New South Wales, Australia, named for Lachlan Macquarie. For a more complete list, see Places named after Macquarie
  • Electoral district of Lachlan, an electoral district of the Legislative Assembly in New South Wales, Australia
  • Electoral district of Lachlan and Lower Darling, an electoral district of the Legislative Assembly in New South Wales, Australia
  • Lachlan River, a river in central New South Wales, Australia
  • Lachlan Shire, a local government area in the central west of New South Wales, Australia
  • Lachlan Valley Railway, a rail preservation society based at Cowra, New South Wales, Australia
  • Lachlan Valley Way, a state highway in New South Wales, Australia
  • Upper Lachlan Shire, a local government area in the state of New South Wales, Australia
• Lachlan, Tasmania, a locality
• Lachlan Fold Belt
• Lachlan Island

Other

• Clan Maclachlan, a Scottish clan which is sometimes known as Clan Lachlan
• HMAS Lachlan (K364), a River-class frigate that served the Royal Australian Navy
• Young Lachlan, a schooner that was stolen and wrecked by convicts in 1819