The following information is from www.orkney.com.
BY FERRY: Northlink Ferries run an overnight ferry between Aberdeen and Kirkwall (Mainland) and between Scrabster and Stromness (Mainland). Click here to connect to the Northlink Ferries website.
Pentland Ferries sail between Gills Bay and St Margaret’s Hope (South Ronaldsay). Click here to connect to the Pentland Ferries website. Foot passengers can also travel on the John O’Groats ferry between John O’Groats and Burwick (South Ronaldsay). Click here to check out their website.
BY AIR: Logan Air offers several flights to Kirkwall (Mainland), from Aberdeen, Edinburgh, Glasgow, Inverness, and Sumburgh (Shetland). Click here to go to the Logan Air website.