Motorcycle trials, also known as observed trials, often called simply trial or trials, is a non-speed event on specialized motorcycles. The sport is most popular in the United Kingdom and Spain, though there are participants around the globe.

Modern trials motorcycles are distinctive in that they have evolved to become extremely lightweight, lack seating (they are designed to be ridden standing up) and have suspension travel that is short, relative to a motocross or enduro motorcycle.

Motorcycle trials are often utilized by competitors in other motorcycle sports (such as enduro, motocross or road racers) as a way to cross-train, as trials requires fine throttle, balance, and machine control.

The event is split into sections where a competitor rides through an obstacle course while attempting to avoid touching the ground with their feet. The obstacles in the course may be of natural or constructed elements. In all sections, regardless of content, the designated route is carefully contrived to test the skill of the rider. In many local observed trials events, the sections are divided into separate courses to accommodate the different skill level of riders, who compete in skill-rated classes.

In every section, the competitor is scored by an observer (hence the sport's name) who counts how many times the competitor touches the ground with the foot (or any other part of the body). Each time a competitor touches the ground with a foot (commonly called "dabs" or "prods"), the penalty is one point.

The possible scores in each section consist of 0, 1, 2, 3, or 5. If a competitor makes their way through the section without touching the ground with a foot, they earn a score of 0 (which is called "cleaning the section"). If they touch the ground once, they receive a score of 1. If they touch down twice, they receive a score of 2. If they touch the ground three or more times, they earn a score of 3—as long as they complete the section without stalling the motor, dismounting, going out of bounds, or going backward. If the competitor fails to complete the section a score of 5 (sometimes colourfully called "a fiasco") is earned. The winner is the competitor with the fewest points at the end of the event. Some events are also timed with penalty points assessed to late riders.

There is a world indoor and outdoor championship, as well as indoor and outdoor national team "world cups" (Trial des Nations). British competitor Dougie Lampkin is notable for winning seven world outdoor titles in the 1990s and 2000s, the same number that Spanish competitor Jordi Tarrés won in the 1980s and 1990s. Previous observed trials greats include Northern Ireland's Sammy Miller (1960s), Finland's Yrjö Vesterinen (1970s) and Belgium's Eddy Lejeune (1980s). The current outdoor world champion is Antoni Bou from Spain who is also the current indoor champion. He has been the sole outdoor and indoor FIM Trial World Championship champion from 2007 to 2024. With these 36 world titles (18 outdoor and 18 indoor), he is the most successful rider in history, surpassing Dougie Lampkin (7 outdoor and 5 indoor) and Jordi Tarrés who is third with 7 outdoor titles.

In addition to the world championship events, there are other major events, such as the Scottish Six Days Trial (SSDT) and the Scott Trial.