On the audio recording posted on the group’s media outlet, a man calls on followers to fight on despite recent defeats.
In the 55-minute statement, he congratulated what he described as the “striking lions” behind recent attacks in Canada and Europe and called on followers to use bombs, knives or cars to carry out attacks.
He also offered greetings to Muslims for Eid al-Adha, a feast which is celebrated this week, suggesting the message was recorded recently.
“For the Mujahideen (holy warriors) the scale of victory or defeat is not dependant on a city or town being stolen or subject to that who has aerial superiority, intercontinental missiles or smart bombs,” the statement said.
“Oh Caliphate soldiers … Trust in God’s promise and His victory … For with hardship comes relief and a way out,” he added, addressing followers in various cities in Syria.
The recording in Arabic was posted by his al-Furqan media group.
The Independent was unable to verify whether the voice on the recording was Mr Baghdadi’s.
Isis, which until last year controlled large areas in Syria and Iraq, has since been driven into the desert by successive defeats in offensives by international allies in both countries.
Mr Baghdadi, who declared himself ruler of all Muslims in 2014 after capturing Iraq’s main northern city Mosul, is now believed to be hiding in the Iraqi-Syrian border region after losing all the cities and towns of his self-proclaimed caliphate.
Isis has claimed responsibility for attacks around the world, including the July shooting in Toronto that left two people dead and 13 wounded. Canadian police said that they had no evidence so far to support the claim.
The man claiming to be Mr Baghdadi also called on Iraqi followers to keep up attacks against Shia Muslims and what he described as apostates – a reference to Sunni Muslims fighting against his group.
He called on followers to remain loyal to the leaders of his movement and urged the citizens of Saudi Arabia, Bahrain and Jordan to overthrow their rulers.
Mr Baghdadi has made only one public appearance, in July 2014, in the al-Nuri Mosque in Mosul, which was retaken by Iraqi security forces in June 2017.
Isis has since released various audio messages that it claims are from Mr Baghdadi, most recently in September 2017.
It appeared to reference news events that happened after Russia claimed he was dead, although the demise of the secretive Isis leader has frequently been reported.
One of his sons was reported to have been killed in the city of Homs in Syria, the group’s news channel reported earlier this year.
Mr Baghdadi also warned that Idlib province in Syria was about to fall as Russia and Syrian government forces were preparing to invade it. Idlib province is in the last swathe of territory still held by rebels opposed to the rule of President Bashar al-Assad.
In June, the United Nations’ regional humanitarian coordinator warned that Isis and other militant groups were mingled with the population in Idlib, making it a highly explosive situation.