Yes. The Prophet ﷺ said, "Every intoxicant is khamr, and every intoxicant is unlawful" (Sahih Muslim 2003), and the ruling is tied to the effect — clouding the intellect — not to the particular plant or chemical, which is why the scholars (Ibn Taymiyyah among them, regarding hashish) applied the prohibition of khamr to narcotics as they appeared in later centuries. Beyond intoxication, these substances cause established bodily and mental harm, and Allah says, "Do not kill yourselves" (Quran 4:29) and "Do not throw yourselves into destruction with your own hands" (Quran 2:195), so the ruling stands even for drugs claimed to be "mild" or legal in a given country. Genuine medical use of a controlled drug prescribed by a trustworthy physician, where there is a real need and no lawful alternative, is a separate matter and is permitted by the scholars, since the prohibition here concerns intoxication for pleasure, not treatment of illness. And Allah's command remains: "Intoxicants... are defilement from the work of Shaytan, so avoid them that you may be successful" (Quran 5:90).
Q&A · Health & Halal Food
Is marijuana or other recreational drug use haram in Islam?
Evidence — the daleel
On deen2u
Informational, not a personal fatwa. Consult a qualified scholar for rulings on your situation.