Matt Mullenweg owns approximately 40-50% of Automattic, according to various sources. This makes him the company’s largest shareholder.
Mullenweg founded Automattic in 2005, and the company has grown to become one of the largest and most successful tech companies in the world. Automattic owns a number of popular products and services, including WordPress.com, WooCommerce, and Jetpack.
Mullenweg has been a vocal advocate for open source software, and Automattic is a major contributor to the WordPress open source project. Mullenweg has also said that he is committed to keeping Automattic a private company.