Motorcycle Trials, also termed Observed 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.

Trial motorcycles are distinctive in that they are 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.

The event is split into sections where a competitor rides through an obstacle course while attempting to avoid touching the ground with the 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 Tarres won in the 1980s and 1990s. Previous observed trials greats include local man Sammy Miller (1960s), Finland's Yrjo Vesterinen (1970s). The current outdoor world champion is Antoni Bou from Spain who is also the current indoor champion.

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

Major current manufacturers of trials bikes are Gas Gas, Beta, Sherco, Montesa, Honda and Scorpa. In the past there have been many manufacturers, from countries such as Spain, Japan, Britain and Italy.

Classic classes exist for vintage bikes. Classes include pre-1965 motorcycles (typically British), events for observed trials motorcycles with two rear shock absorbers. In most cases, twin-shock motorcycles were manufactured before 1985 and are typically Japanese or Spanish. A recent addition has been a class for air-cooled mono shock bikes; this covers machines up to around 1990.

A competition event is called an "observed trial" or "trial" (not plural), unless referred to as an "observed trials event."