It is the second time Putin has written to Charles in recent days, after offering his condolences following the death of Queen Elizabeth II on Thursday.
Russian President, Vladimir Putin, has sent his congratulations to King Charles III as he formally became the new British monarch, despite the King once describing him as being like Adolf Hitler.
Putin in a statement posted on Twitter by the Russian Embassy in London, said: "Please accept my sincere congratulations on your accession to the throne. I wish Your Majesty success, good health and all the best."
The statement is unlikely to be met with anything other than a frosty reception by the Palace as the King had been outwardly critical of the Russian president in the past, particularly for his barbaric actions in Ukraine.
It is the second time Putin has written to Charles in recent days, after offering his condolences following the death of Queen Elizabeth II on Thursday.
He wrote: “The most important events in the recent history of the United Kingdom are inextricably linked with the name of Her Majesty. For many decades, Elizabeth II rightfully enjoyed the love and respect of her subjects, as well as authority on the world stage.
“I wish you courage and perseverance in the face of this heavy, irreparable loss. I ask you to convey the words of sincere sympathy and support to the members of the royal family and all the people of Great Britain.”
For good measure, the Kremlin has also claimed that the queen’s “wisdom and authority” would be missed internationally.
The Russian people had “great respect” for Queen Elizabeth II, Kremlin spokesman Dmitry Peskov told reporters on Friday, singling out her qualities of “wisdom and authority”.
“Such qualities are in very short supply on the international stage at the moment,” he added pointedly.
The brief letter was dated September 10 and comes as the King was officially presented as the new monarch in London on Saturday.