Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND) or Lou Gehrig's disease, is a neurodegenerative disease that results in the progressive loss of motor neurons that control voluntary muscles. ALS is the most common type of motor neuron disease. Early symptoms of ALS include stiff muscles, muscle twitches, and gradual increasing weakness and muscle wasting. Limb-onset ALS begins with weakness in the arms or legs, while bulbar-onset ALS begins with difficulty speaking or swallowing. Half of the people with ALS develop at least mild difficulties with thinking and behavior, and about 15% develop frontotemporal dementia. Most people experience pain. The affected muscles are responsible for chewing food, speaking, and walking. Motor neuron loss continues until the ability to eat, speak, move, and finally the ability to breathe is lost. ALS eventually causes paralysis and early death, usually from respiratory failure.Most cases of ALS (about 90% to 95%) have no known cause, and are known as sporadic ALS. However, both genetic and environmental factors are believed to be involved. The remaining 5% to 10% of cases have a genetic cause linked to a history of the disease in the family, and these are known as familial ALS. About half of these genetic cases are due to one of two specific genes. ALS and frontotemporal dementia (FTD) are considered to be part of a common disease spectrum (ALS-FTD) because of genetic, clinical, and pathological similarities. The underlying mechanism involves damage to both upper and lower motor neurons; in ALS-FTD, neurons in the frontal and temporal lobes of the brain die as well. The diagnosis is based on a person's signs and symptoms, with testing done to rule out other potential causes.There is no known cure for ALS. The goal of treatment is to improve symptoms. A medication called riluzole may extend life by about two to three months. Non-invasive ventilation may result in both improved quality and length of life. Mechanical ventilation can prolong survival but does not stop disease progression. A feeding tube may help. The disease can affect people of any age, but usually starts around the age of 60 and in inherited cases around the age of 50. The average survival from onset to death is two to four years, though this can vary, and about 10% survive longer than 10 years, and death is usually due to respiratory failure. In Europe, the disease affects about two to three people per 100,000 per year. Rates in much of the world are unclear. In the United States, it is more common in white people than in black people.Descriptions of the disease date back to at least 1824 by Charles Bell. In 1869, the connection between the symptoms and the underlying neurological problems was first described by French neurologist Jean-Martin Charcot, who in 1874 began using the term amyotrophic lateral sclerosis. It became well known in the United States in the 20th century when in 1939 it affected baseball player Lou Gehrig (leading to his death two years later), and later worldwide, following the 1963 diagnosis of then 21 year old cosmologist Stephen Hawking. However, unlike most individuals with ALS, Hawking managed to survive his illness for another 55 years. The first ALS gene was discovered in 1993 while the first animal model was developed in 1994. In 2014, videos of the Ice Bucket Challenge went viral on the Internet and increased public awareness of the condition.

Henry Louis Gehrig (born Heinrich Ludwig Gehrig; June 19, 1903 – June 2, 1941) was an American professional baseball first baseman who played 17 seasons in Major League Baseball (MLB) for the New York Yankees (1923–1939). Gehrig was renowned for his prowess as a hitter and for his durability, which earned him his nickname "The Iron Horse". He was an All-Star seven consecutive times, a Triple Crown winner once, an American League (AL) Most Valuable Player twice, and a member of six World Series champion teams. He had a career .340 batting average, .632 slugging average, and a .447 on base average. He hit 493 home runs and had 1,995 runs batted in (RBI). He still has the highest ratio of runs scored plus runs batted in per 100 plate appearances (35.08) and per 100 games (156.7) among Hall of Fame players. In 1939, he was elected to the Baseball Hall of Fame and was the first MLB player to have his uniform number (4) retired by a team.

A native of New York City and a student at Columbia University, Gehrig signed with the Yankees in 1923. He set several major-league records during his career, including the most career grand slams (23; since broken by Alex Rodriguez) and most consecutive games played (2,130), a record that stood for 56 years and was long considered unbreakable until surpassed by Cal Ripken Jr., in 1995. Gehrig's consecutive game streak ended on May 2, 1939, when he voluntarily took himself out of the lineup, stunning both players and fans, after his performance on the field became hampered by an undiagnosed ailment subsequently confirmed to be amyotrophic lateral sclerosis, an incurable neuromuscular illness; it is now commonly referred to in North America as "Lou Gehrig's disease".The disease forced him to retire at age 36, and claimed his life two years later. The pathos of his farewell from baseball was capped off by his iconic 1939 "Luckiest Man on the Face of the Earth" speech at Yankee Stadium.

In 1969, the Baseball Writers' Association of America voted Gehrig the greatest first baseman of all time, and he was the leading vote-getter on the MLB All-Century Team chosen by fans in 1999. A monument in Gehrig's honor, originally dedicated by the Yankees in 1941, currently resides in Monument Park at Yankee Stadium. The Lou Gehrig Memorial Award is given annually to the MLB player who best exhibits Gehrig's integrity and character.