The North Shore Monster, sometimes referred to as "Old Briney," purportedly inhabits the Great Salt Lake in Utah. Descriptions of the monster vary, but it is most commonly described as having a crocodile-like body and the head of a horse.

The most well-known sighting occurred on July 8, 1877, when J.H. McNeil and other workers at the Barnes and Co. saltworks on the lake's northern shore claimed to have encountered a large creature with a crocodile-like body and the head of a horse. McNeil estimated the creature to be about 75 feet long. The creature reportedly let out a loud bellow as it approached the shore, prompting the men to flee into the nearby mountains where they hid overnight. The next morning, they found large overturned boulders and disturbed ground along the shoreline.

McNeil signed an affidavit attesting to the sighting, and the story was published in the Corinne Record and later in the Salt Lake Herald-Republican and the Deseret News. However, the Deseret News suggested that the report should be taken "with a few grains of salt." Some skeptics proposed that the "monster" may have been a buffalo in the lake, although the reported length of 75 feet does not align with this explanation.

In more recent years, new accounts of the monster have emerged. In 2023, State Park Ranger Holly Minor recounted a story about two hunters on Stansbury Island who were reportedly chased into a cave by a creature described as part crocodile, part horse, with a wingspan of over 100 feet. According to the account, the creature returned with an entire cow in its mouth, leaving the hunters to hide in terror overnight.

The legend of the North Shore Monster may have roots in earlier reports. Around thirty years prior to McNeil's encounter, a man identified as Brother Bainbridge claimed to have seen a creature with a dolphin-like body in the lake near Antelope Island. Another official of the LDS church, referred to as Brother Kimball, reported seeing a porpoise in the lake on April 19, 1848. These sightings led to Antelope Island initially being named "Porpoise Island." Some theories suggest that the men may have mistaken large carp swimming in the less salty waters of Farmington Bay for these creature(s).

The Great Salt Lake's salinity fluctuates between 3.5 and 8 times that of the ocean, depending on location and water levels, and has a maximum depth of 33 feet. These extreme conditions limit the types of life that can thrive in the lake, with only a few species such as brine shrimp and brine flies found in the main lake. Carp and other fish species are able to survive in the freshwater wetlands and tributaries surrounding the lake.

Despite the challenging environment, legends about large creatures inhabiting the lake persist. These tales may have been influenced by sightings of unusual phenomena or by misunderstandings of natural occurrences in the lake's unique ecosystem.

In 1976, a short independent horror film titled The Giant Brine Shrimp was produced by Salt Lake local Mike Cassidy. The film depicts a fictional account of a giant brine shrimp terrorizing downtown Salt Lake City. Although the creature in the film is referred to as "Old Briney," it bears little resemblance to the North Shore Monster, as it is portrayed as a massive version of the lake's native brine shrimp rather than the crocodile-like creature described in the original sightings.

• Bear Lake Monster
• Great Salt Lake whale hoax
• List of reported lake monsters
• Living fossils

41°09′N 112°40′W / 41.150°N 112.667°W / 41.150; -112.667