A search is under way for a 14-year-old Melbourne boy who got lost during a family hike in southern Victoria, police say.

Josh became separated from family members on Saturday evening while they hiked Phillips Track in the Great Otway National Park at Wyelangta, about 200km southwest of the city.

Just before 7.40pm, the teenager was spotted by a group of campers and a local farmer near the Aire Crossing campsite – about 7km from where he went missing.

The teen, from Dandenong in Melbourne’s southeast, is about 180 centimetres tall with a slim build and dark brown shaved hair.

He is wearing black shorts, a hooded top and a red cap, police say.

Anyone who has seen him is urged to contact the Apollo Bay police station.