AskKaka lists the STD code of Chennai that is 044. Chennai is a part of Tamil Nadu and the ISO code of Tamil Nadu state is TN.
Chennai STD code aka subscriber trunk dialing code is 044 which is mentioned above on this page of AskKaka. We are great resource of finding Chennai std code of Tamil Nadu (TN).
Useful Info :-
Please take a note that if you are in India and dialing a landline number of Chennai then you will have to dial STD code 044 as a prefix followed by the phone number of a landline user and if you are calling Chennai's phone number from a foreign country then you need to add +91 (the country code) followed by 44, e.g. +9144 (no need to add "0" as prefix) followed by the landline phone number.
Found any error in the detail mentioned above? Please report it to firstname.lastname@example.org