SYDNEY has locked up promising defender Aliir Aliir for a further three years, keeping him committed to the club until the end of 2021.

Aliir, 23, has provided intercept marking and drive out of the Swans' defence.

He struggled in the NEAFL for much of 2017, but the backman has strung together five straight matches in the senior side, and kicked the match-sealing goal in Sydney's round 17 win over North Melbourne at Etihad Stadium, the first goal of his career.

"We are very pleased to announce Aliir's contract extension for a further three years," football manager Tom Harley told

"Aliir has a great story to tell and we see his footy as an exciting next chapter in his life. 

"Since 2016, Aliir has had to overcome some injury challenges but we have seen in the past couple of weeks what he is capable of.

"Aliir is a popular clubman who we see playing an integral role for our club in the future."

Drafted at No.44 in 2013, Aliir rose to prominence in 2016, proving an exciting member of Sydney's defence as the Swans made the Grand Final.

However, a knee injury meant he missed the decider, which the Swans lost to the Western Bulldogs.