The exhibition, Wallace, Bruce and Scotland's Contested Crown, opens at Stirling Castle next month and brings together two manuscripts which provide insight into the different paths taken by the two leaders in securing the Scottish crown.
On display will be a 700-year-old letter from King Philip IV of France to his agents in Rome commanding them to ask Pope Boniface VIII to support Wallace. Written in November 1300, the letter was discovered in the Tower of London in the 1830s and is currently on loan to the National Records of Scotland from The National Archives in London.
In 2011, a panel of experts concluded it was likely to have been in Wallace's possession, although how and why remain unclear.
The Wallace letter will appear alongside a letter to King Philip IV of France. Dating from 1309, it was written by Scottish barons attending the first parliament following Robert the Bruce's seizure of the throne in 1306.
Their declaration of support for Bruce as the rightful king of Scots marked an important moment in the recognition of his crown. The document is preserved in the National Records of Scotland.
Culture Secretary Fiona Hyslop said: "The bringing together of these documents for the first time will provide a fascinating insight into one of the most turbulent periods in Scotland's history.
"This is a fantastic opportunity for visitors to view these rare and special documents which provide a tantalising glimpse into the lives and legacy of two of Scotland's most famous historical figures."
Tim Ellis, keeper of the records of Scotland and chief executive of the National Records of Scotland, said: "The death of Alexander III in 1286 triggered a dynastic scramble that came to a head in 1306, when Robert the Bruce seized the Scottish throne.
"This exhibition brings together for the first time two archival treasures connected to William Wallace and Robert the Bruce, and adds to our understanding of this fascinating period of Scottish history.
"We're delighted to be holding the exhibition which has been made possible through support from Historic Scotland and The National Archives."
The Wallace, Bruce and Scotland's Contested Crown exhibition will form part of a series of events at Stirling Castle which will tell the story of the events leading up to the Battle of Bannockburn, which marks its 700th anniversary this year.