The answer is: Luke

Luke 1:3 / Acts 1:1 - From these two verses it is reasonable to assume Luke wrote Acts.

The book of Acts has long been celebrated as a historical narrative that captures the growth of the early Church and its vibrant spread across the Mediterranean. Credit for this powerful account goes to Luke, a figure whose background as a physician enriches his writing with precision and a keen eye for details.

Interestingly, Luke opens both his Gospel and Acts with a dedication to a man named Theophilus, suggesting that these works may have been intended to provide both structure and context to the early Christian message. The name 'Theophilus' literally means "friend of God," opening up delightful speculation—was this a title, perhaps, for anyone in the early Church seeking enlightenment?

Additionally, Acts is often called “the second part of the Luke-Acts narrative” which invites readers to see them together. While the Gospel recounts the life and teachings of Jesus, Acts picks up the narrative from his resurrection. Fun bit of trivia: Did you know that Luke is the only Gospel writer who includes the story of the Good Samaritan? His focus on compassion for the marginalized underlines a universal message of inclusivity that resonates throughout Acts as the diverse early community embraces both Jews and Gentiles.

Exploring Acts not only deepens our understanding of early Christian history, but it also shows us the dynamic growth of a movement that stood boldly as a testament to love and community, well before doctrinal divisions arose.