The 85-year-old monarch ascended the throne when her father, George VI, died on Feb. 6, 1952. She is the longest-serving monarch after Queen Victoria, who reigned for more than 63 years.
Before a year's worth of festivities to celebrate her milestone, the queen said she and her husband have been "deeply moved" to receive so many kind messages about her Diamond Jubilee.
"I am writing to thank you for the wonderful support and encouragement that you have given to me and Prince Phillip over these years," she wrote in a message to the nation. "In this special year, as I dedicate myself anew to your service, I hope that we will all be reminded of the power of togetherness and the convening strength of family, friendship and good neighborliness, examples of which I have been fortunate to see throughout my reign."
The queen's Diamond Jubilee will be feted with a series of regional, national and international events throughout 2012.
Over the course of 2012, members of the royal family – including Prince William and his wife, the Duchess of Cambridge – will fan out across the globe and travel to Commonwealth countries including Canada, Jamaica and Belize in honor of the queen's Diamond Jubilee.