The lion is an animal that has inspired enormous numbers of people over the centuries. Lions represent many thing because of the long history they've shared with humans while both species were evolving in Africa, so it's no surprise that the lion has worked its way deep into the human psyche. Lions, like other felines (See cat tattoo designs and tiger tattoo designs, have had enough of an impact that their image has significance even far outside of their natural habitat, with lions having prominent symbolic positions in cultures as far away from Africa as China, Japan and Europe.
The most common symbol associated with the lion is bravery and power. Lions are one of the apex predators of Africa and until recently they regularly preyed on humans. This, combined with their size and cunning, has made them symbols of power for nearly every culture that has encountered them or stories about them. In Africa the lion is a symbol for authority and kingship, a trend that spread to Europe as early as the Middle Ages, where they were used for heraldic symbols by Kings and Emperors. Lions even appear in the names of some European royalty; Richard the Lionhearted of the Robin Hood stories is a great example.
Part of the power of the lion as a symbol is doubtlessly a result of the lion's many appearances in Judeo-Christian scripture. Lions reprise their role as a signifier for kingship, being associated with the House of David from which Christ is said to draw lineage (In Christian belief, Jesus is often represented by the Lion of Judah). Lions also feature in the stories themselves, with tales of lions laying down with lambs. Christ himself draws the distinction between the lion and the lamb as a symbol of the new age that dawned with his birth. The long tradition of gladiatorial games featuring lions versus Christians is another potent source of symbolism for lion tattoos.
The Judeo-Christian symbolism of the lion draws from older traditions in the Middle East, dating back to Assyrian, Ancient Egyptian and Mesopotamian traditions. Stone lions adorned temples and palaces, were featured in myth and legend and were central figures tales of greatness. Lions abound in mythology, from Hercules to animist beliefs from Africa. Killing a lion was often the greatest test of a warrior or hero's prowess. And the lion is a central member of the Zodiac under the guise of Leo, which adds a rich body of astrological symbolism to the King of the Beasts.
Lions play many roles in our symbolism, from markers of royalty to challenges for the greatest men to overcome. Their long coexistence with our ancestors in the depths of prehistory means that we are almost predisposed to view them with awe and fear, despite their currently precarious position as a species threatened with extinction. Lion tattoos are ways for humans to symbolize the traits they share with lions, from strength and power to wisdom and altruism.