A day before his highly anticipated appearance before the Royal Commission into Trade Union Governance and Corruption, video has emerged of Opposition Leader Bill Shorten passionately outlining his vision for Australia inside a Sydney pub.

In the video obtained by the ABC, rowdy Labor supporters cheer as an emotional Mr Shorten tells the crowd he dreams of an Australia where same-sex marriage is legalised, Indigenous people are recognised in the constitution, and where "people can organise to have a strong minimum wage and they will not be subject to a royal commission".

The video was filmed in Sydney's Covent Garden pub on Sunday night.

Mr Shorten will appear before the royal commission on Wednesday, where he is expected to face questioning about his time as head of the Australian Workers Union.