In last year's contest, there were more than 18,000 entries to the contest. Photos are divided into four categories:
Entries for this year's contest are being accepted until June 30th. If you think you've got what it takes, enter here.
The grand prizewinner gets an eight-day trip - the National Geographic Photo Expedition: Costa Rica and the Panama Canal - with airfare for two.
To celebrate the end of the contest, National Geographic has shared some of its favorite entries from the "Travel Portraits" category with us here.