T-Mobile US, the second-largest wireless carrier in America, is extremely fortunate to have someone like Mike Sievert at the helm. Sievert has been actively involved in all of T-Mobile’s biggest corporate decisions since he joined the company in 2012. Starting off as chief marketing officer, he helped launch the company’s transformational “Un-carrier” marketing campaign, which sought to rework T-Mobile's public image with a focus on no overage charges, no contracts, unlimited data, and other offerings.

As a result of his success as CMO, Sievert rose to chief operating officer in 2015 and became president in 2018. That same year he joined the board of directors, and he took up the position of CEO in April 2020, following T-Mobile’s $26.5 billion merger with Sprint Corp. Today, Sievert is responsible for a team of roughly 75,000 employees and is widely considered to be a leading figure in the telecom industry.

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Before joining T-Mobile, Sievert worked for a number of large companies inside and outside the wireless industry.

Prior to earning his bachelor's in economics from the Wharton School of the University of Pennsylvania in 1991, he started his career at Procter & Gamble in 1990, one year before he completed his degree. He spent six years of his early career at P&G, later working at IBM and E-Trade, moving up from one position to another.

Then, in 2002, with just over a decade of management experience under his belt, Sievert made executive status when he was hired at AT&T Wireless in the position of executive vice president and chief marketing officer. His next step up on the ladder of success in the business world came in February 2005, when Microsoft brought him on board in the position of corporate vice president of the Global Windows Group. In this role, he led preparations for the release of Longhorn, which was later called Windows Vista.

In addition to his many corporate roles, Sievert is an accomplished investor and entrepreneur. The majority of his efforts in this area have focused on the technology community, including co-founding Switchbox Labs, a startup which was acquired by Lenovo in 2009.

Sievert is also a strong believer in encouraging the young leaders of tomorrow. Joining forces with T-Mobile's previous CEO, John Legere, the pair have sponsored a competition titled “Changemaker," which provides a platform for aspiring entrepreneurs to come up with their own business ideas and then make a pitch for funding.