If you are sure that you don't want to use Steam anymore, you can submit a Steam Support request to terminate your account. Steam Support will ask that you provide comprehensive Proof of Ownership prior to fulfilling the request.
Account termination is permanent. You will not be able to reverse this procedure once Steam Support has processed the request.
No. Once Steam support has terminated the account, it cannot be restored.
Account termination will not result in refunds for purchases made on the account. If you would like to request a refund, please use the Help site.
Your Steam wallet and the funds within it will no longer be available once the account has been terminated.
No, terminating the account does not free up the CD Key to be used on a different account. Once a CD Key has been registered, it cannot be registered again.
Your public profile will be removed. Profile information such as avatars, screenshots, artwork and persona history will no longer be available. If there is anything you wish to save, it must be done prior to termination.
Some community content is not removed upon termination. This includes things like content that you posted in Steam community hubs, as well as comments or posts that you left on other profiles.
Account names can only be used once, regardless of whether an account has been terminated. Email addresses, persona names and purchase information can freely be used on other accounts.
Due to the significance of fulfilling a termination request, Steam Support will require that users provide thorough Proof of Ownership prior to termination of the account in question.