The Doctor Who actor will play Siegfried Sassoon in The Pity of War: The Lives of Loves of the War Poets, a one-off 60-minute drama.
The drama will be centred on the relationship between Sassoon, Wilfred Owen and Robert Graves while they wrote about their war experiences.
It is part of a series of programmes marking the centenary of the outbreak of World War I.
Olivia Colman will narrate a four-part series titled The Great War: The People's Story, which tells the stories of personal accounts collected from archives and libraries.
Alison Steadman, Daniel Mays, Claire Foy and Brian Cox will also feature in the series, alongside others.
"This programme gives the stage to the authentic voice of the British people as they endured over four years of the greatest violence in human history," said Richard Klein, ITV director of factual.
"The diaries, letters and memoirs of privates and officers, wives and mothers, working class and the well-to-do all brilliantly and emotionally document the journey from the patriotism and positivity at the start of the war to the gradual understanding of the deadly and mind-shattering realities of modern warfare to the final days of simple endurance and exhaustion.
"This is a beautifully composed portrait of a country during a war that changed everything for everyone."
Meanwhile, The Pals Army will be a one-off documentary about the million young men who served in the Pals Battalions.
The three programmes will air on ITV from August.