What is science communication for? We argue that science communication can be framed, reimagined and transformed in service of social justice, which is what the papers in this special issue examine. We understand the vocabulary of “social justice” to signal the centring of critical research and practice paradigms, an ethical commitment to righting wrongs, building equity for all human beings and the broader ideal of improving the world [Fraser, 2003; Sen, 2009; Young, 1990]. We argue that bringing critical social justice lenses to science communication can usefully interrogate, rethink and ultimately reshape our field. This special issue examines both critical perspectives on science communication and what equitable transformations might entail.