The King officially marked the first year of his reign on Friday 8 September, as he took the day to remember his late mother, Queen Elizabeth II.
King Charles III issued his first statement as King 34 minutes after the late Queen's death was announced to the world.
He described his mother's passing as "a moment of the greatest sadness".
As plans for Queen Elizabeth II's funeral were put into place, the Privy Council officially proclaimed His Majesty as King Charles III during his historic Accession Council on 10 September.
The late Queen's state funeral took place nine days later at Westminster Abbey, followed by a committal service at St George's Chapel in Windsor.
Since becoming King, Charles has undertaken engagements in 161 days, including travelling to all four nations of the UK and attending dozens of functions, according to PA News Agency.
As HELLO! marks the first year of Charles's reign, take a look back at some of his major milestones from the last 365 days
First Christmas broadcast
© GettyThe King paid a touching tribute to his late mother in a pre-recorded message from St George's Chapel in Windsor, which aired on Christmas Day, as per tradition.
The monarch said: "I am standing here in this exquisite Chapel of St. George at Windsor Castle, so close to where my beloved mother, The late Queen, is laid to rest with my dear father."
It was just three months after the late Queen's death.
He continued: "I am reminded of the deeply touching letters, cards and messages which so many of you have sent my wife and myself and I cannot thank you enough for the love and sympathy you have shown our whole family.
"I am reminded of the deeply touching letters, cards and messages which so many of you have sent my wife and myself and I cannot thank you enough for the love and sympathy you have shown our whole family. Christmas is a particularly poignant time for all of us who have lost loved ones. We feel their absence at every familiar turn of the season and remember them in each cherished tradition."
First State Visit
© GettyThe King's inaugural state visit to Germany in March was dubbed a success and saw Charles deliver the first speech by a British monarch – mostly in German - during a session of the Bundestag.
A trip to France before their German leg was set to become Charles and Camilla's first official state visit, but the trip was shelved at the last minute following riots across the country over pension reforms.
The couple will now carry out their rescheduled state visit to Paris and Bordeaux from 20 to 22 September.
First Easter at Windsor
© GettyThe King and Queen led the royals at the Easter Sunday church service in Windsor, with appearances from some of the youngest members of the family, including the Prince and Princess of Wales's three children and Mike and Zara Tindall's daughters.
First official portrait as King and Queen
A week before the coronation, Buckingham Palace released the first official portraits of Charles and Camilla to mark their reign.
The images were taken in the Palace's blue drawing room by their wedding photographer Hugo Burnand, with one showing the King and Queen, coordinating in blue and standing side by side in front of a portrait of King George V painted shortly after his coronation in June 1911.
Two further images also showed Charles and Camilla seated individually.
Coronation
© GettyThe King and Queen's joint coronation took place at Westminster Abbey in May, in front of 2,500-strong congregation, while over 20 million Brits watched the ceremony on TV.
See all of the highlights from the day in the clip below…
First Trooping the Colour
© GettyIn June, the King marked his first birthday parade of his reign, which saw him joined on horseback by Princess Anne, Prince William and Prince Edward.
It was the first time a monarch has ridden on horseback since the late Queen Elizabeth II rode on her beloved horse, Burmese, in 1986.
Meanwhile, Queen Camilla, the Princess of Wales and Prince George, Princess Charlotte and Prince Louis watched proceedings from a carriage.
Senior working royals joined the King on the palace balcony to watch the flypast.
First summer at Balmoral
© GettyThe King and Queen took up their summer residence at Balmoral Castle in August, and have hosted several members of the royal family at their Scottish home.
Among their guests were the Prince and Princess of Wales, the Duke and Duchess of Edinburgh, the Princess Royal and Vice Admiral Sir Timothy Laurence and the Duke of York.
The pair also attended their first Braemar Gathering Highland Games of their reign, and as tradition, they hosted Prime Minister Rishi Sunak and Akshata Murthy.
King Charles' 75th birthday
© GettyOn 14 November 2023, the King celebrated his 75th birthday.. He marked the occasion by taking part in special events with charitable causes close to his heart.
On the eve of his big day, the King was joined by fellow 75-year-olds for a special party at his countryside abode, Highgrove.
The afternoon tea, featured dancing with live music from a local rock choir, and also marked the 75th anniversaries of the NHS and the Windrush generation in 2023.
On his actual birthday, Charles and Camilla attended a surplus food distribution centre outside London in line with The Coronation Food Project.
The charity seeks to bridge the gap between food waste and food needs across all four nations of the United Kingdom, helping people and helping the planet.
He also held a reception at Buckingham Palace for 400 nurses and midwives, as part of this year's NHS 75 celebrations. He was treated to a performance of a surprise birthday song.
Second Christmas at Sandringham
© ShutterstockThe King hosted his second Christmas at Sandringham in December 2023. He was joined by his fellow family members including his son Prince William and his family.
The senior royals attended a service at St Mary Magdalene Church and the King took the time to speak to some locals within the area who had come out to see him on his way to the church. It looked as though he was enjoying the conversation as he chuckled with the locals.
It was also the King's second Christmas address. This year, Charles addressed the nation from Buckingham Palace, the speech took place in the beautiful Centre Room, which has seen countless senior royals gather ahead of their appearances on the balcony.
The King's prostate operation
© GettyOn 17 January 2024, Buckingham Palace announced the news that King Charles would be undergoing surgery on his prostate. The news of the King's surgery came on the same day Kensington Palace announced that Princess Kate had been admitted to The London Clinic for planned abdominal surgery.
In a statement, the palace shared: "His Majesty's condition is benign and he will attend hospital next week for a corrective procedure. The King's public engagements will be postponed for a short period of recuperation."
It's understood that the King, 75, was keen to share the details of his diagnosis to encourage other men who may be experiencing symptoms to get checked in line with public health advice.
Cancer diagnosis
© Getty ImagesOn 5 February King Charles was diagnosed with cancer. The news was announced by Buckingham Palace who issued an official statement.
It read: "During the King's recent hospital procedure for benign prostate enlargement, a separate issue of concern was noted. Subsequent diagnostic tests have identified a form of cancer.
"His Majesty has today commenced a schedule of regular treatments, during which time he has been advised by doctors to postpone public-facing duties. Throughout this period, His Majesty will continue to undertake State business and official paperwork as usual."
The statement continued: "The King is grateful to his medical team for their swift intervention, which was made possible thanks to his recent hospital procedure about his treatment and looks forward to returning to full public duty as soon as possible.
It is yet to be revealed what type of cancer the King has.
