John Smith, aged 84, was last seen leaving the Crianlarich Hotel at 7.15am on Thursday, August 5.
Mr Smith from Nottingham was driving his grey Mazda 6 estate, registration YD60 RNZ
He is described as being 5ft 10 in height of slim build, with grey hair which is thinning on top.
He was last seen wearing a white shirt, blue jumper, dark coloured jacket, grey trousers, white hat and grey satchel style bag.
The 84-year-old has been described by Police as a ‘keen hillwalker’ and it is believed he was intending to walk in the area of Crianlarich and Oban.
Inspector Andy Angus said: “We are growing increasingly concerned for John and would urge anyone who believes they may have seen either him or his car to get in touch as soon as possible.
“Anyone who may have seen John, or who has any information on his whereabouts, is urged to contact Police Scotland via 101 quoting incident number 0922 of 7 August.”