The Monk

Her fists a blur as they deflect an incoming hail of arrows, a half-elf springs over a barricade and throws herself into the massed ranks of hobgoblins on the other side. She whirls among them, knocking their blows aside and sending them reeling, until at last she stands alone.
Taking a deep breath, a human covered in tattoos settles into a battle stance. As the first charging orcs reach him, he exhales and a blast of fire roars from his mouth, engulfing his foes.
Moving with the silence of the night, a black-clad halfling steps into a shadow beneath an arch and emerges from another inky shadow on a balcony a stone’s throw away. She slides her blade free of its cloth-wrapped scabbard and peers through the open window at the tyrant prince, so vulnerable in the grip of sleep.
Whatever their discipline, monks are united in their ability to magically harness the energy that flows in their bodies. Whether channeled as a striking display of combat prowess or a subtler focus of defensive ability and speed, this energy infuses all that a monk does.

In The Nameless Trilogy World

Meditating in a mountain-top monastery, or calmly walking through the bustling streets of a foreign city, the monk may not seem the most intimidating character. But what they hide behind a calm and relaxed demeanor is a body and mind that has been trained as one in the mystical arts.
Monks can exist in any setting, be it urban or isolated or anywhere in between. Although they are usually found in small cloistered hermitages far away from civilization to allow them time and space to study the art of Ki, which fuels everything that they are able to do. This pursuit of inner wisdom in the ways of Ki drives the monk forward.
As a common trait, monks do not usually distract themselves with things like material wealth or possessions. If they live in the city, they are rarely seen living a lavish lifestyle, choosing instead to live in the poorer districts. They will also be found defending the weak and helpless in the city from those who try to oppress them.

Resources:

• Player's Handbook
• Xanathar's Guide to Everything
• Xanathar's Lost Notes to Everything Else
• Sword Coast Adventurer's Guide

Subclasses:

• Way of the Open Hand (PHB)
• Way of Shadow (PHB)
• Way of the Four Elements (PHB)
• Way of the Drunken Master (XGtE)
• Way of the Kensei (XGtE)
• Way of the Sun Soul (XGtE)
• Way of Atonement (XLNtEE)
• Way of Empathy (XLNtEE)
• Way of the Long Death (SCAG)