SIPTU (/ˈsɪptuː/; Services, Industrial, Professional and Technical Union; Irish: An Ceardchumann Seirbhísí, Tionsclaíoch, Gairmiúil agus Teicniúil) is Ireland's largest trade union, with around 200,000 members.

SIPTU is a general union which organises across the public and private sectors in Ireland and has large numbers of members working in construction, health, education, transport and manufacturing.

It has a long-term commitment to delivering social solidarity and has developed a leadership role in the areas of rights for unemployed persons, people with disabilities and older persons.

The union, as part of promoting fairness at work and justice in society, includes migrant workers in Ireland and campaigns on the twin issues of the exploitation of migrant workers, particularly those from Poland, Latvia and Lithuania, and the consequent displacement of Irish workers from employment.

The union established an Organising Unit in 2004 and its former president, Jack O'Connor, set as his objective the transformation of SIPTU - hitherto firmly committed to a servicing agenda - into an organising union.