Largest city of Pakistan is Karachi
By largest city here we mean city with large number of inhabitants. In other words it will a city where a large number of people lives. The country (Pakistan) conducted its most recent population census in 2017, which revealed the total population of the country to be over Two Hundred Millions. This puts Pakistan on Fifth position in the list of Top Ten most populace countries. Previously the country had Sixth position.
As per the results of 2017 population census of Pakistan, the largest city of Pakistan on the basis of population is Karachi.
Also it is worthy to note that Karachi is the economic hub of the country which is located in Sindh province of Pakistan. It was also the first capital of Pakistan.
Source: Source of above answer is Pakistan Bureau Of Statistics
