The lead violinist in an orchestra is the

The lead violinist in an orchestra is the concertmaster, or the principal first violin.

N an orchestra, the concertmaster is the leader of the first violin section. There is another violin section, the second violins, led by the principal second violin. Anyviolin solo in an orchestral work is played by the concertmaster (except in the case of a concerto, in which case a guest soloist usually plays).