Seal or SEAL may refer to articles connected to a variety of meanings:

A marine mammal
a pinniped, a large ocean mammal. There are three main groups:
Earless seals (or true seals)
Eared seals (or walking seals)
Walrus
Seal hunting, both personal and commercial hunting of seals
Seal brown is a rich dark brown color RGB(50, 20, 20) (from the colour of dyed Fur seal fur)

Fixing or closing to give a tight fit
Seal (mechanical), a device to contain pressure.
Diaphragm seal, a flexible membrane that seals and isolates an enclosure

Symbol of authentication
Seal (device), a device used to produce an official stamp as a symbol of authority, or the impression left by a seal in sealing wax. (Origin: Latin sigillum = "small symbol", a diminutive of signum)
Cylinder seal, cylinder engraved with a picture story, used in ancient times to roll an impression onto a sheet of wet clay
Great Seal of the United States used since 1782 to authenticate some documents issued by the United States government
Great Seal of the Realm, a British institution for authorising the monarch's official documents a personal signature
Great Seal of Scotland allows the monarch to authorise documents without signing
Imperial Seal of Japan, called 菊の御紋 in Japanese, meaning "Noble Symbol of Chrysanthemum"
Lord Privy Seal or Lord Keeper of the Privy Seal is one of the traditional sinecure offices of state in the United Kingdom
Knights Templar Seal used to validate documents approved by the order
Seal of Solomon, a legendary magical signet ring said to have belonged to King Solomon
LMLK seal, stamped on handles of large storage jars around Jerusalem about 700 BC
Nintendo Seal of Quality is a gold seal used by Nintendo to show that a game is properly licensed to run on their game consoles

As a person's name
Barry Seal (Adler Berriman Seal), pilot and drug smuggler turned DEA informant
 Brajendra Nath Seal (born 1864), Indian philosopher of the Brahmo Samaj, Vice Chancellor of Visva Bharati University
David Seal (born 1972), an Australian football (soccer) player
Jaynie Seal (born 1973), an Australian television presenter
Lou Seal (Luigi Francisco Seal, Jr.), the official mascot of the San Francisco Giants team in Major League Baseball
Manuel Seal, a staff songwriter and producer at Jermaine Dupri's So So Def Recordings
Pu Tong Seal (1346 AD), legendary Burmese hero
 Seal (musician) (Henry Olusegun Olumide Adeola Samuel), an Afro-European soul singer who has released three albums named "Seal":
Seal (1991 album)
Seal (1994 album)
Seal (2003 album)

As a place name
Some of these names referred originally to the marine mammal.
 Seal Bay Conservation Park, on Kangaroo Island, South Australia
 Seal Beach, a city in Orange County, California, United States of America
 Naval Weapons Station Seal Beach, a United States Navy weapons and munitions loading, storage and maintenance facility in Seal Beach, California
 Seal Island, a small islet about 5.7 km off the northern beaches of False Bay near Cape Town in South Africa
 Seal Island (South Shetland Islands), a group of small islands and rocks lying 3 to 6 miles northwest of Elephant Island in the South Shetland Islands
 Machias Seal Island at  under disputed sovereignty between the United States and Canada
 Seal Island Bridge, an arch truss bridge crossing the Great Bras d'Or channel in Victoria County, Cape Breton Island, Nova Scotia
 Seal Rock, a prominent rock offshore at the North end of Ocean Beach, San Francisco, United States
 Seal Rocks, a small settlement in New South Wales, Australia
 Seal, Kent, a village in Kent, England. (Origin: probably Anglo-Saxon sēale = "copse of sallow-trees")
 Seals, Georgia

As an acronym
 United States Navy SEALs, special forces of the United States Navy. (Origin: acronym from "SEa, Air, Land")
Advanced SEAL Delivery System, a midget submarine providing stealthy submerged transportation for special forces, primarily U.S. Navy SEALs
SEAL Recon Rifle, rifle developed to provide SEAL snipers with a portable, lightweight system with greater lethality
 Semantics-directed Environment Adaptation Language, a computer programming language
 SEAL (cipher), (Software-Optimized Encryption Algorithm), a fast cryptographic cipher
 Safety Evidence Assurance Level, US government
 SEAL (Computer Language), the Semantics-directed Environment Adaptation Language
 SEAL (Sea Scout Leadership Training), a leadership training course for Sea Scouts youth in the Boy Scouts of America
 Software Engineering and Ada Lab, NASA

Ships
 HMS Seal (N37), a submarine of the Royal Navy
 USS Seal has been used as the name of two submarines of the United States Navy
 Red seal ships (朱印船), Japanese armed merchant sailing ships with a red-sealed patent (early 17th century)

In computers
SEAL GUI, an open source Graphical User Interface for DOS