List of United States elementary school mathematics competitions

National elementary school mathematics competitions

Perennial Math
Continental Mathematics League (CML)
Game-a-thon challenges students to design and build math games in this national contest.
Noetic Learning Math Contests - semiannual problem solving contest for elementary and middle school students. [Grades 2-8]
The Math Bee hosted by the North South Foundation
Math Olympiads for Elementary and Middle Schools (MOEMS) -- An extremely popular competition amongst elementary and middle school students. Website
Math Kangaroo may be the world's largest mathematics competition. Website
Math League has different names in different states and regions.
Math Madness (website) (AoPS Forum) 100% Online league and bracket tournament held in the fall (Mini-Madness held in spring)
Beestar National Competition(BNC) and Weekly Problem Solving Contests - Challenge students of data analysis and problem solving skills in real life math questions. Grade 1-8.
Online Math League (OML)
National Trimathlon is a fun filled Math Competition for kids in grades 3 through 6.
RSM Foundation International Math Contest is a two-round Olympiad-style contest for students in grades 3-8 (website)