The homing pigeon is a variety of domesticated Rock Pigeon (Columba livia) that has been selectively bred to be able to find its way home over extremely long distances. Because any pigeon generally returns to its own nest and its own mate, it was relatively easy to selectively breed the birds that repeatedly found their way home over long distances. Flights as long as 1689 miles have been recorded by exceptional birds in competition pigeon racing. Their average flying speed over moderate distances is around 30 miles per hour, but they can achieve bursts of speed up to 60 mph. Homing pigeons have been used to carry messages written on thin light paper (such as cigarette paper) in a small tube attached to one leg; this is called pigeon post.
This bird is to be distinguished from the carrier pigeon, an entirely different breed.
Some research has been performed with the intention of discovering how birds can find their way back from distant places they have never visited before. Some researchers believe that pigeons navigate by Earth's magnetic field. Near their home lofts, in areas they have previously visited, pigeons probably are guided by natural and artificial landmarks. Research by Floriano Papi (Italy, early 1970s) and newer research published in the February, 2004 issue of Animal Behaviour suggest that pigeons also orient themselves by odors and/or combinations of odors. (See the August 20, 2005 issue of Science News.)
Various experiments suggest that different breeds of homing pigeons rely on different cues to different extents. Charles Walcott at Cornell was able to demonstrate that one strain of pigeons was confused by a magnetic anomaly in the Earth that had no effect on another strain of birds. Other experiments have shown that altering the perceived time of day with artificial lighting or using air conditioning to eliminate odors in the pigeons' home roost affected the pigeons' ability to return home.
Some research also indicates that homing pigeons navigate by following roads and other man-made features, making 90 degree turns and following habitual routes, much the same way that humans navigate .
Messenger pigeons were used as early as 1150 in Baghdad  and also later by Genghis Khan.
In 1850, Paul Reuter, who later founded Reuters press agency, used a fleet of over 45 pigeons to deliver news and stock prices between Brussels and Aachen. The outcome of the Battle of Waterloo was also first delivered by a pigeon to England.
Possibly the first regular air mail service in the world was Mr Howie's Pigeon-Post service from the Auckland New Zealand suburb of Newton to Great Barrier Island, starting in 1896. Certainly the world’s first 'airmail' stamps were issued for the Great Barrier Pigeon-Gram Service from 1898 to 1908. 
They were used extensively during World War I, and one homing pigeon, Cher Ami, was awarded the French Croix de Guerre for his heroic service in delivering 12 important messages, despite being shot once.
Eighty-two homing pigeons were dropped into Holland with the First Airborn Division Signals as part of Operation Market-Garden in World War II. The pigeons' loft was located in London which would have required them to fly 240 miles to deliver their messages.¹
Homing pigeons were still employed in the 21st century by certain remote police departments in Orissa state in eastern India to provide emergency communication services following natural disasters. In March 2002, it was announced that India's Police Pigeon Service messenger system in Orissa was to be retired.
The humorous IP over Avian Carriers (RFC 1149) is an Internet protocol for the transmission of messages via homing pigeon. This protocol has been used, once, to transmit a message in Bergen, Norway.
Notable pigeon enthusiasts in the United Kingdom include Gerry Francis (football manager) and Duncan Ferguson (Everton and Scotland footballer).
In Chinese martial art (wushu) films and dramas, homing pigeons are often used for "Pigeon Mail" (飛鴿傳書). People often labor under the misapprehension that the pigeons know where to deliver the mail. The fact is that they can only go back to one "mentally marked" point that they have identified as their home. So "pigeon mail" can only work when the sender is actually holding the receiver's pigeons.
The Taliban banned homing pigeons (or probably more realistically the keeping of homing pigeons and/or the use for sport) in Afghanistan.
¹ 'A Bridge too Far' by Cornelius Ryan
- An informative magazine article written in the 1880s
- Image of a homing pigeon (Note the straight slope from the top of the head to the beak, and the prominent band around the nostrils. This photograph also shows a message tube and a small sheet of very thin paper near the bird's feet.)
- The three most important things that every pigeon fancier should know
-  (Newspaper article on the '97 pigeon race "disaster")
- Acquiring white homing pigeons
- The System of Military Dovecotes in Europe from an 1891 Scientific American article at Project Gutenberg