Dutch Queen Beatrix is expected to announce later on Monday her abdication in favour of her son after 33 years on the throne, Dutch media reported.
Beatrix, who turns 75 on Thursday, will abdicate "in favour of her son Willem-Alexander," Dutch news agency ANP said, quoting sources close to the court.
The queen is to make the surprise announcement on national television at 7pm (1800 GMT), after which Prime Minister Mark Rutte is to speak.
Beatrix's much-loved mother Juliana also abdicated, in 1980, when her daughter stepped into her shoes at age 42.
Beatrix's abdication will end more than 100 years of female reign on the Dutch throne.
Willem-Alexander (45) is to become the first Dutch king since Willem III, who reigned until his death in 1890.