The 22-year-old joined the League One club midway through the January transfer window after a failed spell at Aberdeen in the first half of the season, where he did not make a single senior appearance.
However, before having the chance to make his debut for Port Vale, it has been revealed that Williams is struggling with an "underlying" injury, and he will head back to Liverpool to undergo his rehabilitation.
"Following the emergence of an underlying injury issue, Rhys Williams has returned to Liverpool to continue his rehabilitation for the remainder of the season," Port Vale said in a statement. "We would like to wish Rhys all the very best in his future career and thank Liverpool for their understanding throughout."
The nature of Williams's injury has not been disclosed, but his time at Aberdeen was hampered a back problem, which also led to complications in his calves.
The former England Under-21 international - who has also spent time on loan with Swansea City and Blackpool - has played 19 times for the Reds' first team since coming through their youth ranks, including seven Premier League starts in the 2020-21 season.
Williams's contract at Anfield runs for another two-and-a-half years until the summer of 2026.