Change ownership of Macintosh HD

I wouldn’t change ownership of the entire Macintosh HD. The macOS system volume is protected, and changing its permissions can cause login, app, or startup problems.

If you’re trying to access a specific file or folder, select that item in Finder, choose File > Get Info, then check Sharing & Permissions. Don’t use “Apply to enclosed items” on Macintosh HD.

What problem or error are you trying to fix? Also, is Macintosh HD your startup disk or an external drive?

Change permissions for files, folders, or disks on Mac - Apple Support

The boot disk should have read-write permission for ‘system’, not any specific user.

The boot disk should have read-only permission for ‘wheel’ and ‘everyone’.

The folders on it may have different permissions. I.e. your home folder would have read-write permissions for that user.

Some basic permissions can be adjusted through the Finder’s “Get Info”﹥Sharing & Permissions.

Power user changes can be made through Terminal (chmod).

If you do it wrongly, you may lock yourself out, or make your Mac vulnerable to processes that shouldn't have wide access.

As the others have mentioned do not try to change any permissions other than the files & folders you created which reside in your home user folder. Even then, avoid changing the permissions on any of the files/folders which by default such as "Desktop", "Documents", etc. or you may cause problems as well.

Why?

As has been mentioned, this is not a good thing to be doing.

Why do you think you need to do it?

Perhaps if you explain what issue you are having that makes you think you need to do this, someone here can offer a different courser of action that does not require messing around with the permissions of the entire volume.