Mathcamp instructors are graduate students, postdocs, professors, and professionals from top universities. We choose instructors who are not only strong mathematicians, but passionate about working with bright students and excellent communicators. Many instructors return from year to year (we get hooked on the magic of Mathcamp, just like the students do!), so alumni will recognize lots of familiar faces.
The faculty live on campus with campers, and you'll interact with them informally outside the classroom: over meals, playing games in the main lounge, and wandering a long trail together on hiking trips, you'll get to know your instructors as mentors (in the true sense of the word).
You can see the list of past summers' faculty (along with some descriptions of their mathematical interests) in the archive of staff.
(And if you're interested in teaching at Mathcamp, check out the job description for grad students!)