Weber, 36, who was serving as interim chief since Chief Ken Massucco retired in March after 37 years with the fire department, was selected to head the 86-member department from a pool of 49 applicants and seven finalists.
Weber was a volunteer with the Schell-Vista Fire Protection District in the Sonoma Valley for 20 years and served as president of the California Fire Exploring Association for the past 10 years.
"I look forward to working with all our communities to ensure Marin remains the safest place to live, work and enjoy," Weber said.
Weber lives in Novato with his wife and two children.
The Marin County Fire Department has six fire stations, two fire lookouts and a 12-member crew. There are 86 employees, 60 seasonal firefighters and 25 volunteers.
The Marin County Fire Department's annual operating budget is approximately $19.4 million.
Weber's salary is $171,954.