Castlevania: Lament of Innocence is a 2003 action-adventure game developed by Konami Computer Entertainment Tokyo and published by Konami for the PlayStation 2 console. Part of Konami's Castlevania video game series, it is the first installment of the series on the PlayStation 2 and the third to make use of a 3D style of gameplay. It was released in Japan and North America in late 2003 and Europe and Australia in early 2004.

Lament of Innocence is chronologically the first game in the Castlevania series. Set in 1094, it focuses on the origins of the series' premise—the eternal conflict between the vampire hunters of the Belmont clan and the immortal vampire Dracula. Lament of Innocence follows Leon Belmont as he searches a vampire's castle in search of his kidnapped betrothed.

Lament of Innocence received generally positive reviews upon release, with praise for the origin story, gameplay, music, and graphics, though some criticized its repetitive level design and excessive backtracking.

The objective of Lament of Innocence is to lead the primary player character and protagonist Leon Belmont through the monster-filled castle as he searches for his kidnapped beloved. Exploring the castle is an open-ended task, with puzzles, concealed items and rooms, and bosses. A room near the castle's entrance contains portals to the five main areas, all of which are accessible from the beginning. After Leon defeats each area's boss, the final area becomes unlocked. Health restoratives and items to improve gaming statistics such as strength and defense can be purchased with in-game money from a shop on the castle grounds.

For his primary weapon, Leon makes use of the Whip of Alchemy given to him by a non-player character, the shopkeeper named Rinaldo. Later on, Leon can acquire three more whips, each guarded by an elemental boss: the Ice, Lightning, and Fire Elemental Whips. Near the end of the game, his Whip of Alchemy turns into the more destructive Vampire Killer. In addition, Leon can combine one of five sub-weapons—a knife, an axe, a cross, a crystal, and holy water—with one of seven orbs to form a special attack. Over the course of the game, he learns special techniques and magic attacks as well.

Two additional player characters can be unlocked: the new character Pumpkin, and Joachim, a vampire who appeared earlier in the game as a boss. Pumpkin makes use of Leon's whip as the primary weapon and only one sub-weapon, has all whip and defensive skills prelearned, and does more damage than Leon. In contrast, Joachim uses five flying swords as his primary weapons; he lacks an inventory and the ability to use relics and purchase items from Rinaldo's shop. However, Joachim has access to two magic attacks in the place of sub-weapons.

Lament of Innocence is set in the fictional universe of the Castlevania series. Set in 1094, it focuses on the origins of the series' premise—the conflict between the vampire-hunting Belmont clan and the vampire Dracula. The protagonist and primary player character of Lament of Innocence is Leon Belmont, a former baron and member of the Belmont clan. His close friend, Mathias Cronqvist, tells him that Leon's betrothed, Sara, is being held captive by the powerful vampire Walter Bernhard. During the game, he encounters Rinaldo Gandolfi, an alchemist and resident of the forest outside Walter's castle.

Arriving on the castle grounds, Leon meets Rinaldo, who gives him a whip crafted by alchemy to assist in killing the monsters and enchants his gauntlet so he is able to use magic relics within the castle. Leon learns that he must defeat five monsters to gain access to Walter's throne room. Arriving at the castle, Leon proceeds to defeat the five monsters, including Joachim Armster, a vampire kept prisoner in the castle by Walter. Before dying, Joachim mentions the Ebony and Crimson Stones, both of which are created from alchemy, and explains to Leon that the Ebony Stone can produce darkness. From Rinaldo, Leon learns that the Crimson Stone converts the souls of vampires into power for its holder.