Dublin Port Company has been the main sponsor of Clontarf Rugby Club since 1994.
The sponsorship will support the continued growth and development of the club and help maintain the club's position as one of the most successful AIB League clubs.
Geoff Curran, Chairman of Clontarf Rugby Club, said: "Dublin Port Company's continued support of Clontarf Rugby Club is essential to help us compete at the top level of club rugby in Ireland and ensures that we continue to attract talented players and coaches and a large active rugby playing membership."
Enda Connellan, Chief Executive of Dublin Port Company, said: "We are delighted to announce the renewal of our sponsorship of Clontarf Rugby Club.
"We have supported the club for the past 15 years and during this time we have seen the club retain its standing as one of the top AIB Ireland League clubs.
"As a company, we are committed to supporting the local community, and we are therefore actively involved in many sporting, educational, socio inclusion and cultural initiatives, to make a positive contribution to the area."