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.
MathCON hosts annual math competition for students in grades 4-12.
Math Madness (website) (AoPS Forum) 100% Online league and bracket tournament held in the fall (Mini-Madness held in spring)
Beestar challenges 1st to 8th grade students in data analysis and problem solving skills through Weekly Problem Solving Contests and Beestar National Competition(BNC)
Online Math League (OML)
National Trimathlon is a fun filled Math Competition for kids in grades 3 through 6.
Pi Math Contest is a math competition for elementary, middle, and high school students.
RSM Foundation International Math Contest is a two-round Olympiad-style contest for students in grades 3-8 (website)
Online Youth Mathematics Competition (OYMC) is a three round contest for students 8th grade and under. There are two divisions: Elementary and Middle School Division. More information can be found in their website (website link)