12 are listed on Wikipedia
C. l. livia, the nominate subspecies, occurs in western and southern Europe, northern Africa, and Asia to western Kazakhstan, the northern Caucasus, Georgia, Cyprus, Turkey, Iran, and Iraq.
C. l. canariensis (Bannerman, 1914) of the Canary Islands, is smaller and is usually darker than the nominate subspecies.
C. l. gymnocyclus (Gray, 1856) from Senegal and Guinea to Ghana, Benin and Nigeria is smaller and very much darker than nominate C. l. livia. It is almost blackish on the head, rump, and underparts with a white back and the iridescence of the nape extending onto the head.
C. l. targia (Geyr von Schweppenburg, 1916) breeds in the mountains of the Sahara east to Sudan. It is slightly smaller than the nominate form, with similar plumage, but the back is concolorous with the mantle instead of white.
C. l. dakhlae (Richard Meinertzhagen, 1928) is confined to the two oases in central Egypt. It is smaller and much paler than the nominate subspecies.
(No photo available)
C. l. schimperi (Bonaparte, 1854) is found in the Nile Delta south to northern Sudan. It closely resembles C. l. targia, but has a distinctly paler mantle.
C. l. palaestinae (Zedlitz, 1912) occurs from Syria to Sinai and Arabia. It is slightly larger than C. l. schimperi and has darker plumage.
(No photo available)
C. l. gaddi (Zarodney & Looudoni, 1906), breeds from Azerbaijan and Iran east to Uzbekistan is larger and paler than C. l. palaestinae with which it intergrades in the west. It also intergrades with the next subspecies to the east.
C. l. neglecta (Hume, 1873), is found in the mountains of eastern Central Asia. It is similar to the nominate subspecies in size, but is darker with a stronger and more extensive iridescent sheen on the neck. It intergrades with the next race in the south.
C. l. intermedia (Strickland, 1844) occurs in Sri Lanka and in India south of the Himalayan range of C. l. neglecta. It is similar to that subspecies, but darker with a less contrasting back.
We are not including the ones noted as derived from the domestic birds.
Those will be listed separately:
C. l. atlantis (Bannerman, 1931) of Madeira, the Azores and Cape Verde, is a very variable population with chequered upperparts obscuring the black wingbars, and is almost certainly derived from feral pigeons.
C. l. nigricans (Buturlin, 1908) in Mongolia and northern China is variable and probably derived from feral pigeons.
My personal belief is that these two should also be considered C. l. domestica.