The former Rangers young gun has penned a three-year deal with the Edinburgh club after spending time on loan at Tynecastle last season and Locke is looking forward to calling on his services on a permanent basis.
"I'm delighted that Danny has decided to sign for the club permanently," the Jambos boss told the club's official website.
"He has a wealth of experience despite only being 21 years old and has already shown how talented he is in his loan spell here.
"I'd like to thank Liverpool for allowing him to come here in the first instance, and Danny himself for showing faith in this club and choosing us when there was interest elsewhere.
"This is the type of player I want to attract to the club and I firmly believe that if he continues to play the way that he can then he'll be called back up to the Scotland squad in no time at all."