Vanneck left TMG last July after two years at the company, to return to The Times as sales and marketing director.
Flanigan will start his new position in early March, and will be responsible for overseeing all of TMG's marketing activities.
Flanigan will report to Michael Moore, Telegraph's executive director of consumer markets.
Moore said: "Barry will be a great asset to the consumer markets team. He will bring with him lots of valuable experience, particularly in the digital arena, and give a refreshing new focus to our marketing efforts."
Flanigan, who joined AOL in 2003, was promoted from director of marketing planning to head of marketing for the UK in March last year, following the company's transition from an internet service provider to a web services company.
Prior to joining AOL, Flanigan held positions at Level 3 Communications and Ovum.
Flanigan said: "I'm looking forward to the challenges that lie ahead as TMG drives forward an innovative multimedia approach. I'm excited to be part of developing marketing strategy across all of the group's platforms."
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