The anti-monarchy group Republic has announced plans for a protest on June 13, the King's Official Birthday.
Trooping the Colour is an annual military ceremony, celebrating the reigning monarch's official birthday.
The occasion is expected to feature over 1,400 parading soldiers, 200 horses, and 400 musicians from the Household Division.
The Royal Family will make an appearance on the famous Buckingham Palace balcony, waving to the thousands of onlookers as the RAF perform their flypast.
Republic, which often embarks on anti-monarchy marches, writes on their website: "Every year, the royals hijack this parade to remain relevant. This balcony moment puts privilege and birth above merit and democracy."
The group staged a protest against the Royal Family on Trooping the Colour last year, where they gathered on The Mall from 6am to make their voices heard during the celebrations.
An official statement from the protest group at the time read: "US citizens have very real concerns about Trump's actions and his military parade.
"Here in the UK, we have the real deal, a king who dresses up in unearned uniforms and medals and insists on a huge military parade through London."
The anti-monarchy group Republic has announced plans for a protest on June 13, the King's Official Birthday
| PAThey slammed: "Trooping the Colour is the key iconic royal event of the year. From now on, there will be protesters there, calling out the event and the monarchy as a superficial cover for a grubby and corrupt institution."
Ahead of next month's demonstration, their website reads: "Last year, attempts were made to keep us out of sight as the royals waved from their balcony. They were clearly rattled by the protest in 2024.
"This year, we won't let that happen. Trooping the Colour is a public event, and we have every right to peacefully protest there."
The demonstrations, which are described as "good-natured and a lot of fun" are expected to congregate at The Mall from 8.30am.
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The Royal Family famously make an appearance on the Buckingham Palace balcony as the RAF perform their flypast during Trooping the Colours
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The King and Queen were met with similar protests earlier this month, when they travelled by horse and carriage to Westminster for the State Opening of Parliament.
The ceremony saw a partly hostile environment for King Charles and his wife, who faced anti-monarchy demonstrations in the streets, with placards being held, asking "Did you know?"
The demonstration, also coordinated by pressure group Republic, questioned King Charles's knowledge of his brother, Andrew Mountbatten-Windsor's, relationship with convicted paedophile Jeffrey Epstein.
King Charles III and Queen Camilla were met with protests on their journey from Buckingham Palace to Westminster for the State Opening of Parliament earlier this month
| GETTYAndrew was arrested on February 19 - his 66th birthday - on suspicion of misconduct in public office. He has consistently denied any wrongdoing in regard to Epstein.
Republic has demonstrated against the monarchy consistently, with Graham Smith, the 52-year-old who leads the protest group, claiming that the death of Queen Elizabeth II "changed everything".
"We suddenly grew, we suddenly went from one member of staff to loads of staff," he previously said.