Ms Westwood, who was the launch editor of Cosmo Bride, is currently fashion editor of Bella.
She will take up her new role on 14 August.
She said: "I am thrilled to be taking up this position.
"Wedding is a magazine that I have always admired, working as I have in the fashion industry over the past few years.
"IPC SouthBank is a prestigious group of titles and I am looking forward to joining them at this exciting time."
Ms Westwood previously worked for six years on national newspapers, rising to fashion editor on The Sun, and as a freelance fashion editor for Now Star Style and Wedding Day.
Publisher Lynsey Bushell said: "I am delighted to welcome Catherine to the Wedding team.
"She is the ideal candidate with expertise in the market and a strong vision for the future development of the titles."
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