The 114-test veteran Younis scored an unbeaten 136 off 279 balls with 14 fours and a six for his 34th test century.
Sydney: Younis Khan made an unbeaten century on Thursday but could not find a reliable batting partner as Pakistan struggled to 271-8 at stumps on a rain-affected third day of the third test against Australia, still needing 68 more runs to avoid the follow-on.
The 114-test veteran Younis scored an unbeaten 136 off 279 balls with 14 fours and a six for his 34th test century, and first in Australia, and provided the only significant resistance by the tourists on a day where four hours were lost to rain.
"(Younis) has been a great servant for Pakistan cricket," opener Azhar Ali said. "It's probably his last tour to Australia so it's a really happy, happy moment for each and every one of us."
Spinner Nathan Lyon took three wickets and fellow slow bowler Steve O'Keefe took one as the hosts pushed toward securing a series clean sweep.
Australia lost wicketkeeper Matthew Wade to illness immediately after the resumption of play and then Matt Renshaw after being hit in the helmet while fielding at short leg, but put aside those setbacks and was buoyed by late wickets.
"Renshaw came off with some headaches and he will be assessed through the night and in the morning," Australia bowling coach David Saker said. "With head knocks you have to take them quite seriously."
Wade was given medication and returned to the team hotel to rest, with hopes he should be fit to play on Friday.
Younis and Azhar Ali added 26 runs to Pakistan's overnight score of 126-2 and looked set to make good progress toward the 338 target to avoid the follow-on before Younis was responsible for a needless run out.
He played the ball to midwicket and called for a quick single, but Mitchell Starc's athletic fielding and throw to Peter Handscomb, who replaced Wade behind the stumps, left Azhar stranded and out for 71.
"It was a key moment in the match," Azhar said. "The spells from Starc and Hazelwood were almost over with the good (batting) time to come around the corner."
"I was looking really forward to that, but unfortunately these things happen."
Azhar has been Pakistan's strongest performer on a tough tour. The opener has 395 runs at an average of 98.75 for the series, surpassing Mohsin Khan's 390 set in 1983 to become the highest Pakistani run-scorer in a series in Australia.
"It's an achievement I am really happy about," said Azhar, who scored 205 not out in Melbourne and 71 in Brisbane also. "It is still one inning to go and I'm really focused that I make it count as well for the team."
Misbah-ul-Haq's poor form this series continued when he lofted Lyon (3-98) directly to substitute fielder Jackson Bird in the deep to be out for 18 off 43 balls, and reduce Pakistan to 178-4.
The Pakistan captain has scores of 4, 5, 11, 0 and 18 at an average of 7.5 in what is likely to be his final series after hinting at retirement at the end of the second test in Melbourne.
O'Keefe (1-37) got his first wicket of the match when his skidding delivery found the inside edge of Asad Shafiq's bat and was well caught by Steve Smith diving to his right after the ball had deflected off Handscomb's thigh.
Next over, Younis brought up his deserved hundred by sweeping Lyon for four off his 208th ball and received a warm reception from the 23,409 SCG-crowd.
"Now he's scored a hundred in each test playing country, so it's a big, big achievement and as a team we are very happy for him," Azhar said.
Starc (1-65) had Sarfraz Ahmed caught by Bird in the gully for 18 in the third over with the new ball and Lyon teased Mohammad Amir into a miscued shot which was caught by David Warner at mid-on.
Josh Hazelwood (2-53) claimed both wickets to fall on day two when he had Sharjeel Khan caught at slip by Matt Renshaw for four and then trapped Babar Azam lbw for a duck four balls later to leave the visitors at 6-2.