Tiger Shark (real name Todd Arliss) is a fictional character, a supervillain in the Marvel Comics universe. He is a recurring foe of Namor the Sub-Mariner.

Todd Arliss was originally a championship American swimmer who was severely injured when he rescued a man who fell overboard. Desperate to regain his swimming ability, he approached a mad scientist, Doctor Dorcas, who 'cured' him by blending his DNA with that of an Atlantean (Homo mermanus) and a tiger shark. The process altered his personality, making him savage, cruel, greedy and predatorial. He subsequently struck out as a villain.

He has committed numerous crimes, including murdering Namor's father Leonard McKenzie. He renounced this life of crime for a time, marrying into a tribe of undersea nomads, but returned to his criminal ways after the tribe, including his pregnant wife, were slaughtered by savage undersea creatures called the Faceless Ones.

During one of his fights with Namor, he also became involved in a battle with Spider-Man also.

Tiger Shark has a sister, Diane Arliss, who is ironically married to a superhero, oceanographer Dr. Walter Newell, who is better known as Stingray.

Tiger Shark has recently mutated, bringing his shark genes to the front: he is now a humanoid shark, with fanged jaws, scaly grey skin and fins.

Tiger Shark wears a tightly-fitting bodysuit with a large fin that runs from the top of his head down his spine. The costume has jagged spines running between the wrist and the elbow as well as all the way down its legs. It has a jagged-edged patch of grey that runs down its center, as well as grey boots and gauntlets. The rest of it is a dull orange, though initially it was red. Water is constantly circulating through the suit, allowing him to maintian peak strength in any situation. After his mutation, Tiger Shark replaced this with a yellow, maskless bodysuit with black bands on the neck, arms and legs.

Tiger Shark is an amphibian humanoid that combines traits of a human, an Atlantean (Homo mermanus), and a tiger shark. He possesses superhuman strength and durability that rivals Namor's own physical ability, but he must be constantly emerged in water in order for him to retain this strength level. Tiger Shark has the amphibious nature and all of the physical capacities of an Atlantean. Before gaining his powers, Todd Arliss was a record-breaking Olympic swimmer, and with his powers he can swim at about 60 miles per hour. He heals extremely quickly and has highly accute senses. He also possesses a hunting instinct inherited from his shark genes; once Tiger Shark locks onto prey, he cannot stop tracking it until he has captured it or been forcibly repulsed. Since his recent mutation, Tiger Shark has gained the ability to deliver powerful bites.

Since his recent mutation, Tiger Shark has a fin on his back which extends over his head, pointed teeth, grey skin, and gills.

Before his recent mutation, Tiger Shark wore a tightly-fitting orange bodysuit with a large fin that runs from the top of his head down his spine. The costume had jagged spines running between the wrist and the elbow as well as all the way down its legs. It had a jagged-edged patch of grey that runs down its center, as well as grey boots and gauntlets. Water was constantly circulating through the suit, allowing him to maintian peak strength in any situation.

After his mutation, Tiger Shark replaced this with a yellow, maskless bodysuit with black bands on the neck, arms and legs.