E21

E21 may refer to:

• BMW E21, an automobile platform
• HMS E21
• European route E21
• DRG series E 21, different locomotives of the German National Railroad
• E21 - Code that it designates the Astronomical observatory of Norm Roses, Leyburn
• E21 - code ECHO of the Nimzo-Indian Defence, opening of chess
• Eyeshield 21, a manga based on American Football
• Economics21, or e21, web portal of the Manhattan Institute for Policy Research
• Kajang–Seremban Highway, route E21 in Malaysia
• The Lotus E21, a Formula One racing car