Harnaut is a city in the Nalanda District of Bihar, India, and the entrance city of Nalanda. The Hindu, Buddhist and Jain pilgrim centres of Nalanda, Pawapuri, Rajgir, Bodh Gaya and Vaishali are all near Harnaut. The incumbent Chief Minister of Bihar, Nitish Kumar, is from Harnaut.
 Harnaut is at an elevation of 49 m (161 ft) above mean sea level (MSL). Harnaut is one of the most prominent block of Nalanda District. It is the gateway city of Nalanda, 55 km from Patna, the capital of Bihar state, and 23 km from the Ruins of Nalanda. It is on the bank of the River Panchane. The land of Harnaut is very fertile. Alluvial soil is deposited by several rivers of the area. There are many local rivers such as the Dhoba, Muhane,Kararua and Panchane. The Ganges River passes nearby at a distance of 10 km.
 Harnaut has a humid subtropical climate in the Köppen climate classification: (Cwa) with hot summers start from early-March to late-June, the monsoon season starts from July to late-August and chilly winter nights and foggy or sunny days from November to February. The climate is not much hot in summer. Harnaut summer's highest day temperature is in between 30 °C to 42 °C. The average temperature in January is 13 °C, February is 19 °C, March is 25 °C, April is 30 °C, May is 32 °C.
 The table below details historical monthly averages for climate variables.
 At present this city does not have municipality, but it is under Sabnahua Panchayat. The people of this city are demanding it to be made into a subdivision. In 2016, the Government of Bihar issued a draft order converting Harnaut into a Nagar Panchayat combining nine villages - Sabnahua, Rupuspur, Porai, Cheran,  Basti, Srichandpur and Dihri.
 The incumbent chief minister of Bihar,  Mr. Nitish Kumar, has been elected many times as MLA from Harnaut legislative assembly seat. His native village Kalyan Bigha is 4 km north-west of Haranut. 
River Muhane passes 1 km west of the city.
 The population of city is around 176140[citation needed]. It is divided into many parts: Beechli Bazar,Chandi road,Gonawan road, Ranchi road,,station road and Harnaut-Athmalgola Rd. Administrative offices are in Dakbanglow Road. Dakbanglow Road is linked to High School Harnaut, Middle School Harnaut, many tuition centres, a big playground and guest house. Beechli Bazar (Central Market Rd), Gonawan road and Chandi Rd is the commercial area of Harnaut. This city is linked to several small roads like - Sartha Rd, Dehra Rd, Swedah Rd, Dwarka Bigha Rd, Gokulpur Rd etc. A small bus stand and a green grocery is located just beside the NH-31.
There is a Carriage Repair Workshop under East Central Railway near NH-30A for POH of 50 Non-AC coaches per month.
 Agriculture is the main source of income, with rice, wheat, pulses, fruits and vegetables being the main crop.[citation needed] There is also one railway coach factory located in Harnaut.[citation needed] Agriculture is the primary activity although tourism in nearby places like Nalanda, Rajgir and Pawapuri boosts economy of this town.[citation needed] This town supplies agricultural products like cauliflower, potato, mustard seed and other vegetables to neighbouring states.[citation needed] Although the economy is mainly based on agricultural products, garments are also manufactured in household industries.[citation needed]
For the help of farmers, there is Krishi Vigyan Kendra, Harnaut which provides help to the people of Nalanda district.
 The city's population is predominantly Hindu with minor Muslim and Christian population. Jains, Sikhs and Buddhists are also present because of the most important place for the Buddhism & Jainism near Rajgir, pawapuri.
For Islamic religion City Mosque, for Christian Loyola Catholic Church and for Hinduism Ramjanki Temple, Mahaveer Temple and more.
 Sweets are present in most restaurants as the popularity has increased.  Many commercial stores have been established as solely desserts stores.
Balushahi prepared in Bihar State especially in Harnaut. Ras malai, rasgulla, gulab jamun, and many more.
 Panipuri "Bhaiya, thoda spicy kam rakhna". Bhelpuri a snack which is a meld of papadis, puffed rice, sev, onions, potatoes, tomatoes, chillies, coriander leaves and chutneys. Kachori with jalebi, Litti (cuisine), samosa, chaat, chole bhature delicious street foods of Harnaut.
 Kebab, biryani, Indian Omelette, chilli chicken/prawn/fish/mutton/vegetables/paneer. Garlic egg/chicken/prawn/fish/mutton/vegetables/paneer. Manchurian, consisting of chicken or vegetables in a spicy sauce. It is entirely a creation of Chinese restaurants. A little resemblance to traditional Chinese cuisine.
Chow mein A popular dish combining noodles, vegetables, scrambled egg, ginger and garlic, soy sauce, green chili sauce, red chili sauce and vinegar.
 Paratha, aloo gobi, baingan bharta, naan, palak paneer, Rajma are the special cuisine of city.
 Harnaut is well connected by roads to different cities. NH 30A connects it to Varanasi, Patna via Fatuha to Sheikhpura district, Barbigha, Barh, Deoghar etc. Harnaut thus serves as the gateway of the Nalanda district to central and southern Bihar. Similarly, NH 31 connects it to Ranchi via Hazaribagh, Barhi, Nawada, and to northeastern India from Mokama, Purnia, Kishanganj up to Guwahati.
 Harnaut railway station is the main railway station of the city, under Danapur Division of the East Central Railway zone. Harnaut is connected with the major cities in India like New Delhi, Mughalsarai, Lucknow, Asansol, Howrah by the Howrah-Delhi Main Linewith daily passenger, express and super fast trains services. Harnaut railway station lies on the Bakhtiyarpur-Gaya main line. This is firstly Bakhtiyarpur-Rajgir Line and the line is being further expanded to Natesar to connect with Gaya junction via Tilaiya junction. A daily government bus services for Biharsharif to Barh via Harnaut.