Laughing Lion was the ship on which Gerion Lannister sailed during his quest to find Brightroar, the ancestral Valyrian steel sword of House Lannister. It is possible the ship was named after Gerion's father, Lord Tytos Lannister, who was known in the westerlands as "the Laughing Lion".
Brightroar was lost by Tommen II Lannister, King of the Rock, when he went in search of plunder during the Century of Blood after the Doom of Valyria. Centuries later, Gerion Lannister hoped to return Brightroar with any other treasures that might have survived the Doom. The Laughing Lion left Lannisport in 292 AC and almost nothing is known about its fate afterwards.
Lord Tywin Lannister sent men to search for the Laughing Lion and his brother. The only trace they could find was in Volantis, where the crew deserted and Gerion had been forced to buy slaves, since no free man would willingly sign aboard a ship sailing to the Smoking Sea. What happened afterwards is unknown. The ship with Gerion and the crew are presumed lost at sea.