In rock climbing, mountaineering, and other climbing disciplines, climbers give a grade to a climbing route or boulder problem, intended to describe concisely the difficulty and danger of climbing it. Different types of climbing (such as sport climbing, bouldering or ice climbing) each have their own grading systems, and many nationalities developed their own, distinctive grading systems.

There are a number of factors that contribute to the difficulty of a climb, including the technical difficulty of the moves, the strength, stamina and level of commitment required, and the difficulty of protecting the climber. Different grading systems consider these factors in different ways, so no two grading systems have an exact one-to-one correspondence.

Climbing grades are inherently subjective. They may be the opinion of one or a few climbers, often the first ascensionist or the authors of a guidebook. A grade for an individual route also may be a consensus reached by many climbers who have climbed the route. While grades are usually applied fairly consistently across a climbing area, there are often perceived differences between grading at different climbing areas. Because of these variables, a given climber might find a route to be either easier or more difficult than expected for the grade applied.