Having been at the club since 2005, Williams has now been handed the top job by manager Tony Mowbray, who revealed the respect in which the Australian is held at Boro
Australia international Rhys Williams has been appointed captain of Championship club Middlesbrough for the 2012-13 season.
The long-serving defensive utility signed a new deal at the North-east club in January, despite interest from a host of English Premier League clubs.
The Western Australian's loyalty has been rewarded, with the Boro academy product handed the appointment by manager Tony Mowbray after former captain Matthew Bates left the club on a free transfer.
"First and foremost he is a top football player with good communication skills and he's very, very well respected in the dressing room," said of Williams, who is on international duty with Australia ahead of Wednesday's international friendly with Scotland.
"He's still developing, yet an immensely talented player and one I hope by giving him the added responsibility of captaincy will be one who will focus his mind on the job week in, week out.
"He had some injury problems early in his career, but has come through them and come out the other end and shown his qualities."