The Whale Track app was made possible by a grant of more than £79,000 from the Heritage Lottery Fund and is available to download to Apple and Android phones and tablets for free.
The app is designed to work in areas with little or no network coverage, so that boat operators, fishermen and other seafarers can share their sightings, and coastal communities and visitors can report their sightings from land.
Of the 92 whale, dolphin and porpoise species in the world, 24 have been spotted off the coast of western Scotland. The app includes a guide to help people identify the marine life they see.
All the scientific data collected by the app feeds into a web portal, allowing anyone to see what sightings have been reported and where.
Registered users will also be able to upload photographs.
Dr. Lauren Hartny-Mills, the charity’s science officer, said: "Whale Track is an exciting innovation that will help to gather crucial data that will improve our understanding of local species of cetaceans – especially coastal species such as bottlenose dolphins and rarer ones including killer whales and humpback whales – and inform policies to safeguard them.
"By using the technology most of us carry around in our pockets, Whale Track makes recording and submitting sightings of marine mega-fauna more convenient and accessible to everyone. This is important in an area that is difficult to monitor because of the nature of the remote coastline."
Whale Track has been developed by the mobile app company Natural Apptitude.
Lucy Casot, head of HLF Scotland, said: "Our natural heritage is a most precious resource and, thanks to National Lottery players, Heritage Lottery Fund grants have helped to protect an amazing range of landscapes, habitats and species of plants and animals.
"HLF is delighted to support the Whale Track app, which will stimulate people’s interest in the marine wildlife along Scotland’s west coast and help them conserve it for future generations."