The Queen's Christian beliefs have been described as the bedrock of her "duty, devotion and service" to others throughout her 60-year reign.
In a thanksgiving service sermon to mark her Diamond Jubilee, the Archbishop of Armagh, the Most Rev Alan Harper, also praised the Queen's groundbreaking visit to the Republic of Ireland last year, which dramatically advanced Anglo-Irish relations.
Her conciliatory words and gestures had allowed many to throw off the "shackles" that had been loosening since 1998's Good Friday Agreement, and to "positively" be themselves, he said.
A congregation of 700 filled the pews of St Macartin's Cathedral in Enniskillen, County Fermanagh, to hear the Archbishop's sermon to the Queen, Duke of Edinburgh and other distinguished guests including Northern Ireland First Minister Peter Robinson.
The town was the scene of a devastating IRA bomb attack in November 1987 which killed 11 people during a Remembrance Day service, and the Queen will meet relatives of victims later in the day.
The Queen and the Duke of Edinburgh arrived in Northern Ireland earlier for a two-day visit whose start was delayed by almost an hour after bad weather forced the Royal Flight to divert from Enniskillen to Aldergrove Airport, near Belfast. On Wednesday a historic handshake will take place between the Queen and Sinn Fein's Martin McGuinness in Belfast.
Speaking about the planned meeting, Mr McGuinness, Stormont's Deputy First Minister, said: "This is about stretching out the hand of peace and reconciliation to Queen Elizabeth who represents hundreds of thousands of unionists in the north."
The Archbishop, head of the church of Ireland, drew parallels between the Queen and her ancestor, Elizabeth I, who addressed Parliament in 1601.
He described how the monarch said in her 17th century speech: "'And though you have had, and may have, many princes more mighty and wise sitting in this seat, yet you never had, nor shall have, any that will be more careful and loving'.
"In that, the first Queen Elizabeth was mistaken. She did not anticipate the reign of her Elizabethan successor for whose 60 years of duty, devotion and service we say 'Thanks be to God'."