The suicide bombing in the city left 22 people dead - including children - and 59 injured as they left a pop concert by US singer Ariana Grande at Manchester Arena.
Her Majesty said in her message of support: "I know I speak for everyone in expressing my deepest sympathy to all who have been affected by this dreadful event and especially to the families and friends of those who have died or were injured.
She also thanked emergency services "who have responded with such professionalism and care" to the "act of barbarity".
Police have confirmed they've arrested a 23 year old man in connection to last night's attack.
Islamic State has claimed it was behind last night's attack in Manchester.
In a statement on social media, the terror group said one of its soldiers had "placed bombs among the crowds".
The Queen added: "I would like to express my admiration for the way the people of Manchester have responded, with humanity and compassion."
The first victim has been named as Georgina Callander, who was a sixth form student at Runshaw College in Lancashire.
The second victim was confirmed to be eight year old Saffie Roussos.
