Lowth will join the company on July 4 after stepping down from his position as chief finance officer at the energy company in the wake of its £35bn takeover by Royal Dutch Shell.
The appointment comes after BT announced that long-serving finance director Tony Chanmugam would take up a new role overseeing the integration of mobile phone giant EE into BT after their £12bn tie-up in January.
Lowth - who has also held top-level positions at drugs giant AstraZeneca and utilities provider ScottishPower - said he was joining the company at an "exciting time".
He added: "Having acquired one of the UK's leading mobile operators and with super-fast fibre broadband available to well over 24 million homes, BT is well-placed for growth in consumer, business and wholesale markets."
Lowth joined ScottishPower in 2003 and worked as the company's corporate strategy director before being promoted to finance director in 2005.
He also worked as chief finance officer for AstraZeneca and served as the company's interim chief executive from June to September 2012, before joining BG Group in November 2013. He has been a non-executive director of Standard Chartered bank since 2010.
One of his key tasks as the company's incoming finance head will be to help manage BT's £12.5bn buyout of EE, which handed the telecoms firm 35% of the mobile consumer market and a similar share of the UK's consumer broadband business.
The deal will also mean BT will be able to offer bundles of telecoms, TV, broadband and mobile to its customers to compete better with rivals such as Sky and Virgin Media.
However, the company ruled out scrapping the EE brand as part of the takeover when it announced its results for the third quarter at the beginning of February.
BT said during a trading update last month that its results were ahead of expectations, as it bolstered reported pre-tax profits by 24% to £862m in the third quarter to December 31 2015.