World Junior Championships (also Youth World Championship as opposed to Senior World Championship) may refer to:
Artistic gymnastics: Artistic Gymnastics Junior World Championships
Association football (soccer): FIFA World Youth Championship, now known as the FIFA U-20 World Cup (also U-17)
Athletics: IAAF World Junior Championships in Athletics
Badminton: BWF World Junior Championships, a tournament organized by the Badminton World Federation (BWF) to crown the best junior badminton players (under-19) in the world
Bandy: Youth Bandy World Championship
Bandy World Championship Y-19
Bandy World Championship U-23
Baseball: 18U Baseball World Cup (also 15U, 12U), the 18-and-under baseball world championship, International Baseball Federation, World Baseball Softball Confederation
Basketball: FIBA Under-19 World Championship
Boxing: AIBA Youth World Boxing Championships, a boxing championship event organised by the AIBA for "Youth" competitors who are between the age of 17–19 years old. It is biennially competition which began in 2008 in Guadalajara, Mexico
Bridge: World Junior Teams Championship, a bridge competition for zonal teams of players up to about 25 years old
Pairs and individuals: World Junior Pairs Championship
Chess: World Junior Chess Championship (U20), an under-20 chess tournament (players must have been under 20 years old on 1 January in the year of competition) organized by the World Chess Federation (FIDE)
World Youth Chess Championship (U18, U16, etc.), a chess competition for girls and boys under the age of 8, 10, 12, 14, 16 and 18. Twelve world champions are crowned every year
IFSC Climbing World Youth Championships
Curling: World Junior Curling Championships, an annual curling bonspiel featuring the world's best curlers who are 21 years old or younger
Fencing: Junior World Fencing Championships (U20), an annual international fencing competition held by the International Fencing Federation for athletes up to 20 years old. They are organised at the same time and venue as the Cadet World Championships held for athletes up to 17 years old
Figure skating: World Junior Figure Skating Championships
Golf: Junior World Golf Championships, held in San Diego, California, United States each year, currently in July
Hockey (field): Men's FIH Hockey Junior World Cup or Women's FIH Hockey Junior World Cup
Hockey (ice): IIHF World Junior Championship; see also U18 men's and U18 women's
Judo: World Judo Juniors Championships
Lacrosse (box): World Junior Lacrosse Championship;
Netball: World Youth Netball Championships, the world championships of netball for national U21 teams, with all players being aged 21 years or younger
Orienteering: Junior World Orienteering Championships
Ski orienteering: Junior World Ski Orienteering Championships
Rhythmic gymnastics: Rhythmic Gymnastics Junior World Championships
Rowing: World Rowing Junior Championships, an international rowing regatta organized by FISA (the International Rowing Federation)
Rugby (union): IRB Junior World Championship
Skiing (alpine): World Junior Alpine Skiing Championships
Skiing (Nordic): FIS Nordic Junior World Ski Championships
Speed skating: World Junior Speed Skating Championships
Short track: World Junior Short Track Speed Skating Championships
Squash: World Junior Squash Championships, the official junior tournament in the game of squash conducted by the World Squash Federation (WSF)
Synchronized skating: ISU World Junior Synchronized Skating Championships
Synchronized swimming: FINA World Junior Synchronised Swimming Championships
FINA Youth World Swimming Championships
Table tennis: ITTF World Youth Championships
Wrestling: World Junior Wrestling Championships, annual event in freestyle and Greco-Roman wrestling held by the United World Wrestling since 1968 for competitors 15–18 years old