Motorcycle trials, also termed observed trials, is a non-speed event on specialized motorcycles. The sport is most popular in the UK and Spain, though there are participants around the globe including Canada and the United States.

Trial motorcycles are distinctive in that they are extremely lightweight, lack seating (they're designed to be ridden standing up) and have suspension travel that is short yet supple, relative to a motocross or enduro motorcycle.

The event is split into sections where a competitor (men, women and children of all ages) 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 his or her way through the section without touching the ground with a foot, a score of 0 (called "cleaning the section") is earned. If he or she touches the ground only once, the score of 1 is earned. If he or she touches down twice, the score of 2 is earned. If he or she touches the ground three times or more, the score of 3 is earned—as long as the section is completed without stalling the motor, dismounting, going out of bounds or going backward. If the competitor fails to complete the section a score of 5 is earned. The winner is the competitor with the least 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. Previous observed trials greats include Northern Ireland's Sammy Miller (1960s), Finland's Yrjö Vesterinen (1970s), Spain's Jordi Tarres (1980s and '90s). The current outdoor world champion is Antonio 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-Day 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 or -1967 motorcycles (typically British), as well as newer vintage 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 monoshock bikes, this covers machines up to around 1990.