Terra Prima Organic Reserve by The Fladgate Partnership, owners of the port house Fonseca, will be launched into the UK off-trade next month priced at £11 for a 75cl bottle.
Grapes for the port are grown in the Pinhão Valley in Portugal from an organically farmed vineyard.
A specialist distiller with the ability to produce high quality organic fortifying spirit, which could be approved by the Port Wine Institute, was the last stage in the process.
It is one of the first organic ports to be produced in the Douro region, based on knowledge obtained from the long-term management of a plot that has been organically farmed at Fonseca's Quinta do Panascal since 1992.
Port brand manager Sarah Woodward said: "It's really exciting for us as there's really nothing else out there in this market. We hope to sell it not only through our existing customers but also through organic or local independent specialists."
Woodward said the product has a similar style to its Fonseca Bin 27, a reserve ruby style of port. "The organic version has a slightly fresher and more aromatic character, and will be priced only slightly higher, about £1 more."
Organic port is not easy to produce, partly due to problems with vine disease and a lack of nutrients in the soil in the Douro region, both of which often require treatment or fertilisers.
A spokeswoman for Mentzendorff said the company has always been a pioneer in its field. "It was one of the first to bring out a white port and now one of the first with organic. It has a history of being a leader."
Terra Prima, which will be packaged in a distinctive bottle to match others in the Fonseca portfolio, will be launched into the UK next month and will be on display on Mentzendorff's stand at the London International Wine & Spirits Fair.