They are Artemis Intelligent Power, for its wind turbine power innovations; Endomag, for its breast cancer diagnostic system; and Victrex, for its advanced materials technology.
They will now compete for a gold medal and the £50,000 cash prize, with the winner being announced on 16 July 2015 at the Academy's annual awards dinner in London.
Edinburgh-based Artemis Intelligent Power has developed a digital hydraulic power system that not only enables offshore wind turbines to generate much more power, but also overcomes reliability issues associated with existing turbines.
"By combining the intelligence of digital control with the robustness and low cost of hydraulic machines, the Artemis team of engineers has made a fundamental advance in the scale and efficiency of mechanical power transmission," states Artemis managing director Niall Caldwell (pictured).
Meanwhile, Cambridge-based Endomag has pioneered a breast cancer diagnostic tool that avoids the use of radioactive tracers in determining cancer spread in the lymphatic system. Its SentiMag probe identifies sentinel lymph nodes for removal by detecting a magnetic, rather than radioactive, tracer signal.
"Endomag is extremely honoured by this recognition, both for the hard work of our founding team and how we have since translated this engineering innovation to meet the needs of so many patients," comments Endomag chief executive Dr Eric Mayes.
Finally, Blackpool-based Victrex is famed for creating the highest performing ultra-thin polymers in the world. Initially enabling smartphone speakers and earbuds to produce high-quality sound without risk of failure, they could now unlock the flexible electronics revolution.
"Victrex is a world leader in high performance polymers and to be in the running for the MacRobert award is a real testament to the capability, innovation focus and performance of our people," says John Grasmeder, technical director at Victrex.
"Each of this year's finalists has demonstrated remarkable drive and determination to achieve technical advances that can make a considerable difference to many aspects of our lives," reflects Dame Sue Ion DBE FREng, chair of the MacRobert Award judging panel.
"The variety and standard of engineering skills behind each innovation is testament to the UK's strength in the sector."
The MacRobert Award is judged by a panel of 10 representing a broad spectrum of engineering enterprise, and each leader in their own right.
The award, which has been running since 1969, is renowned for spotting the 'next big thing' in technology.
Last year's winner, SME Cobalt Light Systems, won for its innovation behind an airport security liquid scanner that can now be found in over 65 airports throughout Europe.