Step 1: Understand the question.
The question asks for the landmark Supreme Court case that definitively established the Right to Privacy as a Fundamental Right under the Indian Constitution.
Step 2: Recall the context.
For many years, the status of the right to privacy was ambiguous. While earlier cases like Kharak Singh and Govind discussed it, they did not give it the status of a full-fledged fundamental right.
Step 3: Identify the landmark case.
The definitive judgment came in 2017 in the case of Justice K.S. Puttaswamy (Retd.) v. Union of India. A large nine-judge constitutional bench of the Supreme Court was formed to decide this specific issue.
Step 4: Know the verdict.
The court unanimously ruled that the Right to Privacy is an intrinsic part of the Right to Life and Personal Liberty guaranteed under Article 21 of the Constitution. This historic judgment overruled previous decisions to the contrary and cemented privacy as a fundamental right of every Indian citizen.