Yes. Even though the United States has not held a draft since 1973, every male citizen of the United States still is required to register for the United States Selective Service within thirty days before or after his eighteenth birthday. Females are not required to register for the Selective Service System. All males between the ages of 18 and 26 who are not citizens of the United States also must register, unless they have legally entered the country as non-immigrants. Although it may seem unusual, illegal aliens still are required to register for the Selective Service.
You may be exempt from registering if you are already on full-time active duty with the U.S. Armed Forces, but part-time duty with the National Guard or Reserves does not exempt you from registering.
If for some reason you do not register when you are 18, you should register as soon as possible. The federal government will not prosecute you if you register before criminal action against you has been started. But if the federal government finds you first, it may be a different story. For failing to register, you could be convicted of a federal crime punishable by up to five years in prison and a fine of up to $250,000! If you need even more reasons to register, those who fail to do so are ineligible for federally-funded student financial aid, civilian jobs with the federal government, and federal job training programs.