An Aggravated DUI, DWI, OUI, or OWI (driving under the influence, driving while intoxicated, operating under the influence, or operating while intoxicated) is the criminal offense of DUI/DWI/OUI/OWI—with additional aggravating circumstances that enhance or make the offense a greater crime—resulting in greater potential punishments.

Aggravating circumstances that may result in an Aggravated DUI/DWI/OUI/OWI charge include (1) a blood alcohol concentration (BAC) that is significantly higher than the legal limit; (2) an accident in which a person is injured or killed, or in which there is property damage; (3) a minor child in the car being transported by the alleged intoxicated driver; (4) driving 20 mph or more over the speed limit; (5) the driver is under the legal age for drinking (generally 21); (6) refusing to submit to a chemical test of blood, breath, or urine; and (7) prior convictions for DUI/DWI/OUI/OWI.

Laws regarding the definitions and names of alcohol and drug-related driving offenses—including the consideration and definitions of aggravating circumstances—vary from state to state and are usually located in a state’s statutes—often in the penal code or criminal code.

In Montana (MT), an Aggravated DUI is a more serious offense than a standard DUI, reflecting the presence of certain aggravating factors. Under Montana law, a DUI becomes 'aggravated' when circumstances such as a high BAC significantly above the .08% legal limit, causing an accident with injury, death, or property damage, having a minor in the vehicle, excessive speeding, or having prior DUI convictions are present. Specifically, Montana Code Annotated § 61-8-465 outlines the penalties for an Aggravated DUI, which include increased fines, longer jail sentences, and the possibility of mandatory treatment programs. For instance, a first-time Aggravated DUI offender may face a fine of up to $1,000, imprisonment for up to one year, or both. Additionally, the presence of a minor in the vehicle can lead to a charge of Endangering the Welfare of a Child under § 45-5-622, which carries its own penalties. Refusing to submit to a chemical test can result in a driver's license suspension under Montana's implied consent laws. It's important to note that the specific consequences for an Aggravated DUI can vary based on the number of prior offenses and the particular circumstances of the case.