There are several things named Alt, including

Abbreviations (TLAs)

• ALT is an abbreviation for alanine transaminase, an enzyme in the liver.
• ALT is also the name of a band, the members of which are Andy White (Irish Musician), Tim Finn and Liam O'Maonlai .
• ALT is also an abbreviation for Assistant Language Teacher, the job title of people on the JET Programme.
• ALT was also an acronym by the NASA for the Approach and Landing Tests of the Space Shuttle in 1976.
• ALT can mean alternative lengthening of telomeres, a mechanism (other than telomerase) that cells use to maintain telomere length.
• ALT, in computing, is a key that often toggles the menu bar of an application.
• ALT is also the german term for "old".

River

• the River Alt, a river in Merseyside.

People

• Franz Alt, German political activist and journalist.
• Carol Alt, American model.

• Der Alte was a popular nickname for German politician Konrad Adenauer.

Internet

• the Alt hierarchy.

Video games

• "alt" is slang for alternate character, a secondary character a player of MUDs or MMORPGs has created for role-playing purposes.

Transportation

"Alt" is an abbreviation or an Alternate Route of a highway.

Beer

• Altbier is a variety of German ale (beer)