Birmingham-based barrister set St Philips Chambers will merge with specialist shipping and international commercial set Stone Chambers.
From August 1, they will be known in London and internationally as St Philips Stone Chambers.
Avtar Khangure QC, head of chambers at St Philips, said: "The merged set will see our national presence combine with Stone's reputation in London and overseas.
"Be they domestic or international, our clients will benefit from a wider-ranging collection of legal services and expertise offered across our offices, combined with the client-first approach which is at the heart of our business."
Stone heads of chambers Elizabeth Blackburn QC and Vasanti Selvaratnam QC added: "We are delighted to be joining forces with St Philips which has a well-established and respected commercial group.
"The merger will put us in the enviable position of being part of one of the largest sets in the country, with all the support and infrastructure that comes with that, while continuing to provide our boutique service in shipping and international commercial disputes."
The merged set will have members based in London, Birmingham, Leeds, the US, Singapore, Hong Kong and Brunei.