THE HAGUE — Dutch Queen Beatrix said Monday that she will abdicate on April 30 after 33 years as head of state, clearing the way for her eldest son, Crown Prince Willem-Alexander, 45, to become the nation’s first king in more than a century.

The announcement, in a nationally televised speech, signaled an end to the reign of one of Europe’s longest-serving monarchs, whose time on the throne was marked by tumultuous shifts in Dutch society and, more recently, by personal tragedy.