Alcohol is the oldest drug known to man, and also the most widely-used drug. So, I would imagine it is the most widely-abused drug, as well.
oxycontin
Marijuana is definitely the most widely used illegal drug in the US. Marijuana is the most widely used illegal drug.
cocaine
Smoking And Alchahol
This is more of a opinion type of question, but the general public would be against it as it's the world's most widely used (and abused) recreational drug, next to caffeine.
Stimulants, in the form of caffeine (coffee and tea). These drugs can produce the desired wakefulness, alertness and sense of well-being, but can also produce cardiac arrhythmias, tremors, insomnia, as well as withdrawal symptoms for some people. The second most widely abused group of drugs are the nicotine containing substances - cigarettes, cigars, and chewing tobacco. The most widely used illegal drug is marijuana (except where it can be obtained legally, for medical purposes, in nearly a third of the states of the United States).
Pharmies... Aka pharmaceuticals.
By a substantial margin, alcohol is the most widely abused drug in every age group—including children. However, marijuana is the most widely used illicit substance among all age groups, but “club” drug use is increasing.
Alcohol is the most widely abused depressant.
Legal drug: Nicotine or alcohol Illegal Drug: Marijuana or cocaine These results were from the US and Canada, answers could change if a broader study was available.
Crack cocaine and nicotine, in that order.