Monk

Players Handbook (page 30)

Monks are monastic aesthetics who practice rigorous mental and physical training and discipline in order to become superior. Therefore they must always be lawful in alignment, although they can be evil, good, or neutral with respect to their approach to lawfulness. A monk who for any reason loses this lawful alignment loses all monk abilities and must begin again as a first level character. Non-player character monks will be aligned as follows: 50% lawful good, 35% lawful neutral, 15% lawful evil.

House Rule

You cannot be one as a player character. There isn't the opportunity in the region where the campaign starts for a player character to learn or be taught the skills of a monk.