Obelisk, a tall, four-sided stone shaft that gradually tapers to a pyramidal point at the top. Ancient Egyptian obelisks are monolithic, cut from a single block of stone. Modern obelisks, such as the Washington and Bunker Hill monuments, are built of many stones.

The earliest obelisks were small and squat. They originated in the Egyptian Old Kingdom (about 2700–2160 B.C.) as symbols of the cult of the sun god Re. At the beginning of the Middle Kingdom, about 2000 B.C., Senusert I erected one of the first large obelisks. Large obelisks were usually placed on bases, or pedestals, in pairs on both sides of temple entrances. The pyramidal summits were often covered with gold, copper, or electrum (an alloy of gold and silver) Obelisks usually also served to commemorate the achievements of a pharaoh's rule. Hieroglyphs inscribed on the four sides of the obelisk described events and listed the elaborate titles of the pharaoh Obelisks have helped scholars to fix the order and duration of the pharaohs' reigns.

Most large obelisks were made of a single piece of red granite from the quarry at Aswan Ancient mural reliefs show the were transported down the Nile River on large barges Many obelisks were erected at Karnak, Luxor, and Heliopolis. Among those still standing in Egypt are those of Queen Hatshepsut and of Thutmose III at Karnak.

The Roman emperors removed many obelisks to Rome. The tallest obelisk known, now in the square of St. John Lateran Church, Rome, is 105 feet (32 m) high.

In modern times, many obelisks were brought to European countries. An obelisk from Luxor dominates the Place de la Concorde in Paris. Two obelisks are called Cleopatra's Needles, although they have no connection with Cleopatra. One is in New York City's Central Park and the other in London.