Brown will join the executive committee and report directly to group chief executive Antony Jenkins.
She joined Barclays in 2011 from BP, and has previously held senior roles at Cable and Wireless and led her own consultancy business.
Antony Jenkins, group chief executive, Barclays said: "Irene has demonstrated her commitment and ability to lead an HR function which can support the business as we deliver the Transform agenda and embed our new purpose and values throughout Barclays."
Brown said: "Every organisation's success depends on the decisions you make around people: who you recruit; how you reward performance; development of your talent; and retention are all crucial to organisational performance.
"I'm relishing the challenge of leading the Barclays HR function as we deliver the changes to the business and its culture that we have promised."
The appointment is subject to regulatory approvals.
