Numerous characters on Lost have tattoos, although they may not have been explicitly referenced.

Characters with tattoos

Character Description Image(s)
Bryan sports a tattoo of two Japanese kanji, yuu + ki, on his right shoulder. Yuuki means "courage, boldness, daring, brave spirit, brave heart." It is actor Charles Mesure's actual tattoo. See http://www.imdb.com/media/rm1292733696/nm0582351 IMAGE
Charlie (as well as the actor who portrays him) bears a tattoo on his left shoulder which reads "Living is easy with eyes closed". This is a quote from The Beatles' song "Strawberry Fields Forever," a song whose lyrics and/or meaning could be considered symbolic of the Losties' experiences, Charlie's in particular. For further dissection of "Strawberry Fields Forever," see its Songfacts page. Also, in the FST the next line "Misunderstanding all you see" is tattooed right below it. CharlieTattoo.jpg
Charlie is seen in "Walkabout" to have a tattoo of the symbol for "nine" in Quenya, a fictional language from J.R.R. Tolkien's Middle-earth cosmology. Dominic Monaghan got this tattoo after playing Merry in all three of Peter Jackson's Lord of the Rings films, as did the eight actors who portrayed the other members of the Fellowship of the Ring, minus John Rhys-Davies. LOTR Tat.jpg
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Cunningham sports a tattoo on his left wrist. The tattoo appears to be either a circular or ovular design. Cunningham tattoo.png
Main article: Jack's tattoos

Jack has various tattoos, one on his left shoulder, one on his back, and a third on the left forearm, at least one of which was placed by Achara in Phuket, Thailand. ("D.O.C.")
Main article: Juliet's mark

Juliet is branded by the Others. ("Stranger in a Strange Land")
Keamy has a tattoo on his left shoulder seemingly consisting of a winged figure loosely resembling a bird. Keamystats2.jpg
On his right shoulder, Keamy has a tattoo of a red (bear?) claw overlaid with a curving symbol - all within a black, compass-like circle. This is similar to the logo used by Blackwater Worldwide, a private military company based in North Carolina.
Naomi has a tattoo on her right shoulder. It was first visible when she was healing at the beach camp, in "The Brig". From what is seen, it appears to be chain-like in design; there is a line running through four individual squares.

This tattoo belongs to actress Marsha Thomason, and can be seen in the TV series "Las Vegas" in at least one episode, "Good Run of Bad Luck" (Season 2, Episode 5).
Tom sports a tattoo on his chest. It has not been referenced, but was barely visible in "Live Together, Die Alone, Part 1" on Tom's upper left pectoral. It appears to be circular with a green, possibly clover-shaped object in the center. Tomstats.JPG
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William Kincaid
Locke's physical therapist, William Kincaid, has a tattoo of six Chinese characters on his left forearm. 3x13 Kincaid tattoo.png