Mount Martha is a seaside town in Melbourne, Victoria, Australia 60 kilometres (37 mi) south-east of Melbourne's central business district. Its local government area is the Shire of Mornington Peninsula. It is on the south-eastern shores of Port Phillip and offers a bathing beach. A boardwalk winds its way for more than 5 kilometres (3 mi) along the Balcombe Creek, its North beach mouth to the Briars Historic Park. The suburb's highest point bears the area's name and reaches 160 metres (520 ft). The peak was named after Martha Lonsdale, the wife of the colonist William Lonsdale.
It marks the start of the Selwyn fault, a geological formation which runs to the eastern Dandenong Ranges.