Which one out of the following is least urbanized state of India?

The correct option is Himachal Pradesh.

According to the Census of India 2011, urbanization levels vary significantly across different states. Urbanization is measured by the percentage of a state's total population living in urban areas. Let us examine the urbanization rates for the states given in the options:
1. Goa: It is one of the most urbanized states in India, with approximately 62.2% of its population residing in urban areas.
2. Maharashtra: It has a high level of urbanization, with about 45.2% of its population living in urban settings.
3. Rajasthan: It has an urban population of approximately 24.9%.
4. Himachal Pradesh: It has the lowest level of urbanization among all Indian states, with only about 10.0% of its population living in urban areas, while the remaining 90.0% lives in rural areas.

Therefore, Himachal Pradesh is the least urbanized state among the given options (and in India as a whole).