Mr Jansen will join the company on 1 January 2019, and will take over the top spot on 1 February after a handover period.
He is joining from payments services group Worldpay, where he will step down as co-chief exec at the end of the year. He has led the group since 2013, overseeing its float on the stock market in 2015.
Jan du Plessis, chairman of BT Group said Mr Jansen “is a proven leader with outstanding experience in managing large complex businesses”.
“Philip's strong leadership has inspired his teams, successfully transformed businesses across multiple industries and created significant value for shareholders. His most recent success at Worldpay, a technology-led business, means he is well suited to build on the solid foundations that are in place at BT,” he added.
In his new role, Mr Jansen will be paid an annual salary of £1.1m, which has been fixed for five years. He also stands to bring home a yearly bonus of up to 240 per cent of his salary, or £2.64m, as well as a long-term incentive share plan award of 400 per cent of his salary.
In June, Mr Patterson said he would step down from BT, weeks after the company unveiled plans to cut 13,000 jobs in a bid to cut costs.
He came under fire when he received a pay rise and a £1.3m bonus two weeks after the lay-offs were announced.
Mr du Plessis said: “I'd like to thank Gavin for his continued leadership of the business and express my gratitude for his commitment and the good progress made over the last few months.”
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies