Timothy was a younger companion of the apostle Paul, first mentioned in Acts 16; two New Testament letters (1 Timothy and 2 Timothy) are addressed to him.
Acts 16:1-2 in the King James Version reads:
1 Then came he to Derbe and Lystra: and, behold, a certain disciple was there, named Timotheus, the son of a certain woman, which was a Jewess, and believed; but his father was a Greek: 2 Which was well reported of by the brethren that were at Lystra and Iconium.
These verses introduce Timothy at the opening of Acts 16. Read it in context at Acts 16:1-2, or the full chapter at Acts 16. Encyclopedia entry: en.wikipedia.org/wiki/Timothy.