Prysmian will design, manufacturer, supply and install cables to connect 110 of the 165 turbines with the offshore substation, it said.
The 300km of 66kV inter-array cables will be delivered in 2021.
The submarine cable cores will be produced at Prysmian’s facility in Wrexham, Wales. The factory will require an upgrade to produce the cables.
Armouring and assembling processes will be performed at the supplier’s Norwegian facility, Prysmian added.
"This key investment in our Wrexham facility is a sign of the growth of the UK offshore wind supply chain, and our strategic ambitions in the renewables industry," said Prysmian offshore sales team manager, Alessandro Panico.
"This order represents around two years of production for this facility, and will benefit other companies that want to deliver competitive local content in their UK projects," he said.
Ørsted’s Hornsea Project Two programme director, Duncan Clark, added: "Further development of a robust, competitive supply chain is needed to provide for UK projects, and to take advantage of exporting abroad as the industry continues to grow globally.
"Working with Prysmian to secure locally manufactured cable cores is just one of the ways we are engaging with suppliers to ensure our wind projects have the highest viable proportion of UK content."
The 1,386MW Hornsea Project Two is due online in 2022. It will feature 165 Siemens Gamesa SG-8.0-167 turbines.
Ørsted secured a contract for difference (CfD) support deal of £57.50/MWh (€64.10/MWh) for the site in the UK’s second auction round in September 2017.