Read Uncommitted is the lowest isolation level in database management systems. It allows transactions to read data that has been modified but not yet committed by other transactions. This means that a transaction can see changes made by others even if those changes might be rolled back later. While Read Uncommitted offers high performance and reduced locking, it comes with risks. The main issue is the potential for dirty reads, where a transaction reads data that could change before it is finalized. This can lead to inconsistencies and unreliable results in applications that require accurate data.