Police are appealing for witnesses to an incident on a bus between Kettering and Burton Latimer.
A 17-year-old girl was travelling on a bus from Kettering to Burton Latimer at about 7.30pm on Wednesday, November 23, when a man reached over and touched her knee.
A police spokesman said: “The man is described as about 50-years-old, 5ft 10in, clean shaven with grey hair in a dreadlock style.
“He was wearing a dark jacket, camouflage trousers and a grey beanie hat.”
Witnesses or anyone with information can contact police on 101 or Crimestoppers anonymously on 0800 111555.