Cardinal George Pell, one of the most powerful figures in the Vatican and Australia's most senior Catholic, has been charged over historic sex assault offences.

In a stunning decision certain to rock the highest levels of the Holy See, police in the Australian state of Victoria said there were multiple charges against Cardinal Pell and the case involved “multiple complainants”.

Cardinal Pell, who intends to return to Australia to clear his name, is the Vatican's de facto treasury minister and is the highest-ranking Vatican official to be charged with sexual abuse.

"I am looking forward finally to having my day in court. I am innocent of these charges," Cardinal Pell said at a press conference at the Vatican early on Thursday morning. "They are false. The whole idea of sexual abuse is abhorrent to me," he added.

Police have not yet revealed the details of the charges but said the cardinal was required to face Melbourne Magistrates Court on July 18.

The Vatican put out a statement on Thursday about the case. "The Holy See has learned with regret the news of charges filed in Australia against Card. George Pell for decades-old actions that have been attributed to him.

"Having become aware of the charges, Cardinal Pell, acting in full respect for civil laws, has decided to return to his country to face the charges against him, recognizing the importance of his participation to ensure that the process is carried out fairly, and to foster the search for truth.