Scotland's First Minister Nicola Sturgeon is joining Labour leader Jeremy Corbyn at a rally in opposition to the UK Government's Trade Union Bill.
About 2,000 people are expected to attend the rally at the Glasgow Royal Concert Hall organised by the Scottish Trades Union Congress (STUC).
STUC general secretary Grahame Smith will open proceedings followed by a speech by Glasgow MP Chris Stephens, who is convener of the SNP trade union group and a senior Unison activist.
Lawyer Aamer Anwar and Labour MSP Jenny Marra will also address the rally alongside another un-named "special guest".
Stop the War in Glasgow have put a call out to anti-war activists to form a picket line outside the Royal Concert Hall to relay their message to the leaders attending the rally.
The rally comes after the Scottish Government formally asked Holyrood to stop Conservative trade union reforms in Scotland.
However, the UK Government insists the Scottish Parliament does not have the power to halt the reforms.
The SNP administration has lodged a legislative consent memorandum to Holyrood to withhold consent for the Bill.
The UK Government does not legislate on devolved matters without the consent of Holyrood but it says the measures in the Trade Union Bill are entirely reserved.
The Scottish Government says it will have an impact on devolved functions and believes legislative consent should be required.