Ryan has been loaned from Brighton, where he has fallen out of favour, but theĀ agreement does not include an option to buy.

The Australian stalwart will be a back-up to Arsenal's first-choice 'keeper Bernd Leno andĀ will go straight into Arsenal's squad for their FA Cup fourth-round clash against Southampton on Saturday.

"Buzzing to be beginning this new chapter and will give everything I've got to contribute to the first club I ever loved," Ryan, a lifelong Arsenal fan, posted on Twitter.

Ryan last featured for Brighton on December 14. with Arsenal managerĀ Mikel Arteta rapt to sign the 28-year-old.

"We know Mat very well through his performances with Brighton in recent seasons and he brings additional quality to our squad," Arteta said.

"Mat has very good Premier League experience and has played over 100 times in the league, which is something that will benefit us greatly on and off the pitch."

Ryan played 121 games for Brighton but was told by manager Graham Potter that Spaniard Rob Sanchez would be given an extended run for the remainder of the season.

"Mat has been a great servant to the club in the Premier League and and he has played no small part for the club at this level," Potter said.

"We have incredible talent and competition at this club for just one position and understandably, as Australia's number one, Mat wants the chance of more regular opportunities."