Voting began at 7 a.m., across 25,874 polling booths in the Maharajganj, Gorakhpur, Kushinagar, Deoria, Bansgaon, Ghosi, Salempur, Ballia, Ghazipur, Chandauli, Varanasi, Mirzapur and Robertsganj constituencies.
There are a total of 42 candidates are in the fray whose fate will be decided by 2.32 crore voters 1.26 crore male and 1.06 crore female.
In 2014, the Bharatiya Janata Party (BJP) and their allies had won all the 13 seats. But the saffron party lost the prestigious Gorakhpur seat in the 2018 by-polls.
The BJP is facing a direct challenge from the Samajwadi Party-Bahujan Samaj Party (SP-BSP) alliance on 10 seats while two - Kushinagar and Deoria - are in for a triangular contest with the Congress. Congress with its ally is contesting on 12 seats.
The saffron party is contesting on 11 Lok Sabha seats in the seventh phase, while its ally Apna Dal (Sonelal) is contesting in Mirzapur, currently held by Union Minister Anupriya Patel, and Robertsganj.
Prime Minister Narendra Modi is re-contesting from Varanasi. Besides Modi, 25 other candidates are in fray from Varanasi. Modi's main challengers are Congress' Ajay Rai and SP-BSP's joint candidate Shalini Yadav.
Among other major contestants are BJP's Uttar Pradesh unit chief Mahendra Nath Pandey, Union Minister Manoj Sinha and Congress R.P.N Singh.
The BJP has fielded Bhojpuri actor Ravi Kishan as its candidate from Gorakhpur.