Porter, who has been working in the role on an interim basis, takes up the position permanently in January.
She will report to chief commercial officer David Pempsel and will have a focus on driving up subscriptions and brand extension opportunities.
The Guardian reported a circulation of 203,592 in November, of which 46,898 were through subscriptions.
Prior to The Guardian, where she has been working for the past five months, Porter was interim chief marketing officer at brand asset management company Adgistics.
Before this she was commercial marketing director at ITV for five and a half years.
She is currently a non-executive director for the Direct Marketing Association, and in the past, was a non-executive director for Freeview and Thinkbox.