The Lake Michigan Triangle is, according to modern legends, an area of Lake Michigan where a number of disappearances, shipwrecks, and plane crashes have occurred under unexplained circumstances. Unidentified flying objects (UFOs) and unidentified submerged objects (USOs), have also allegedly been spotted in the area. The triangle stretches from Ludington to Manitowoc, down to Benton Harbor, and back to Ludington. The first major unexplained event was the disappearance of the French sailing ship Le Griffon and her crew in the 17th century. Starting with the sinking of the Thomas Hume In 1891, shipwrecks and disappearances became more frequent. This trend may be attributable to better record keeping or to increasing population in the area. The first reported UFO sighting was in 1913.

The frequency of disappearances, shipwrecks, and plane crashes within the Great Lakes was first mentioned in Jay Gourley's 1977 book, titled The Great Lakes Triangle. Although the exact origin of the Michigan Triangle is unknown, later authors focused on occurrences in Lake Michigan, particularly those within the bounds of the triangle.

Some experts have debated about the shape and range of the triangle. One argued that the area is not a triangle, but a rectangle, or oblong shape, that fills most or all of Lake Michigan.

The Lake Michigan Shipwreck Research Association claims that the triangle is a myth, contending that the triangle has no more shipwrecks than the rest of the Great Lakes. They also stated that the number of shipwrecks within the Great Lakes can be attributed to the high traffic over the lakes.

Many of the shipwrecks and ship disappearances in Lake Michigan have been blamed on wind waves. Due to the lake's elongated shape and position, its shores are parallel and unimpeded, allowing the formation of dangerous currents including riptides and longshore tides. Additionally, the north-south orientation coupled with regular wind patterns allow waves to reach great heights.

Another common theory for the disappearances is magnetic anomalies caused by magnetic declination and magnetic deviation. Declination refers to the difference between true north and magnetic north, which differs depending on location. On average, Lake Michigan deviates four to five degrees westward. Deviations are errors induced in compasses by local magnetic fields. For example, if you were to hold a compass near a magnetic object, the needle would point towards the object instead of magnetic north. Although this would not be a problem in vehicles with other navigational equipment, it could cause confusion to inexperienced sailors and pilots.

Conspiracy theorists have blamed the triangle on a negative energy vortex. Energy vortexes are the idea that certain locations emit sacred, powerful, and transformational energy. Although vortexes are typically considered to promote positivity and healing, it's claimed that vortexes with negative-energy also exist. These locations are purportedly sources of danger and malevolence. Ley lines, areas that intersect ancient structures and landmarks, are often cited as causes of energy vortexes. According to ley line maps, one runs down the middle of Lake Michigan. Others attribute the triangle's supposed vortex to a prehistoric structure under Lake Michigan discovered by archaeologists in 2007. The site is often referred to as the "North American Stonehenge."

Others believe the occurrences in the Lake Michigan Triangle are caused by aliens, pointing to UFO sightings as evidence.