Algernon Sidney, English philosopher and politician, Lord Warden of the Cinque Ports (born 1623)

Algernon Sidney or Sydney was an English politician, republican political theorist and colonel. A member of the middle part of the Long Parliament and commissioner of the trial of King Charles I of England, he opposed the king's execution. Sidney was later charged with plotting against Charles II, in part based on his most famous work, Discourses Concerning Government, which was used by the prosecution as a witness at his trial. He was executed for treason. After his death, Sidney was revered as a "Whig patriot—hero and martyr".

Lord Warden of the Cinque Ports is the name of a ceremonial post in the United Kingdom. The post dates from at least the 12th century, when the title was Keeper of the Coast, but it may be older. The Lord Warden was originally in charge of the Cinque Ports, a group of five port towns on the southeast coast of England formed to collectively supply ships for The Crown in the absence of a formal navy at that time. Today, the post is a sinecure and an honorary title, and 14 towns belong to the Cinque Ports confederation. The title is one of the higher honours bestowed by the Sovereign; it has often been held by members of the Royal Family or by prime ministers, especially those who were influential in defending Britain in times of war.