Holder joins Inspire from Azamara Cruises where she most recently held the role of International Marketing Manager with the line.
Taking up a new post as Social Media Lead, she will work closely with Inspire's Head of Product, Marketing and Commercial, Claire Dutton, to "provide leadership" across the agency's social media activity while contributing to wider marketing efforts.
Holder joined Azamara from Not Just Travel, where she was Head of Trade. Prior to that, she was UK Trade Partnership Manager at Hurtigruten and has previously held the roles of both Head of Marketing and Head of Trade at The Travel Network Group.
Inspire Chief Executive Lisa Henning said: "Since Claire joined us nine months ago, she has been conducting a thorough review of our needs across the product, marketing and commercial areas of the business, aligned with the significant growth we've seen across Inspire.
"This is to ensure we resource these important areas in the right way to keep pace and continue delivering for our partners, whilst also providing further investment and support to our 100-strong team of independent travel associates.
"Bringing new talent into our business is central to our growth strategy. Natalie's appointment is a great example of that. Her experience across the travel sector makes her a fantastic addition to the team, and we're delighted to welcome her."
Holder added: "Inspire has achieved a great deal over the past few years, and with Lisa's ambitious vision for the future, I'm genuinely excited to be part of the next chapter.
"My focus will be on driving forward the group's social media strategy, as well as working closely with Inspire's team of homeworkers and helping them leverage their local marketing activities to support their business growth."