Sports boot including a shell and a liner, the shell extending upward so as to at least partially surround the lower leg of a user and including at least one tightening device configured to tighten the lower leg of the user. The tightening device includes the following: a first strap portion attached to the shell using a first anchoring mechanism; a second strap portion; mechanism configured to pair the first strap portion with the second strap portion; adjusting mechanism configured to adjust the length of the first strap portion or the length of the second strap portion; and a second anchoring mechanism configured to optionally connect the second strap portion to the shell.