Central Coast Mariners Football Club is an Australian professional association football club based in Gosford, on the Central Coast of New South Wales. It competes in the A-League Men, under licence from the Australian Professional Leagues (APL).

The Mariners were founded in 2004 and are one of the eight original A-League teams. It is the first professional sports club from the Gosford region to compete in a national competition. Despite being one of the smallest clubs in the league, the Central Coast Mariners are one of the most successful clubs in Australian soccer history, having won three A-League Championships from six Grand Final appearances and topped the table to win the A-League Premiership three times. The club has also appeared in the AFC Champions League five times and won the AFC Cup once.

The club plays matches at Central Coast Stadium, a 20,059-seat stadium in Gosford; its purpose-built training facility, Mariners Centre of Excellence, is located in the suburb of Tuggerah. The facility is also home to a youth team that competes in the A-League Youth. The Mariners' main supporters' group is known as the Yellow Army, for the colour of the club's home kit. The club shares a rivalry with Newcastle Jets, known as the F3 Derby, after the previous name of the highway that connects the cities of the teams. Matt Simon is the Mariners' all-time leading goalscorer as of May 2022, with 66 goals in all competitions. The team record for matches played is held by John Hutchinson, who has appeared in 263 games for the Mariners.

Central Coast Mariners' bid for a franchise in the Football Federation Australia's new A-League competition was aimed at filling the one spot for a regional team that was designated by the FFA. Media speculation prior to the announcement of the franchises in the new league suggested that the Mariners' bid may be favourable due to its new blood. Backing from former Australian international player and club technical director Alex Tobin, as well as Clean Up Australia personality Ian Kiernan—who would act as inaugural club chairman—also strengthened its proposal. As the only regional bidder, Central Coast was expected to make it into the league by default. Following a reported signed deal with the FFA, the club signed former Northern Spirit coach Lawrie McKinna as manager and Ian Ferguson, a former Rangers and Northern Spirit player, as coach. To aid the FFA's goals of building the profile of the sport, the Mariners created formal links with local state league team Central Coast United. On 1 November 2004, after much expectation, the club was announced as one of eight teams to become part of FFA's domestic competition, the A-League. The decision made Central Coast Mariners the first Gosford-based professional sports team to play in a national competition.

At the time of the formation of the new league in 2004, the club was owned by Spirits Sports and Leisure Group. The club announced its search for a star player under the league's allowance for one star player outside of the $1.5 million salary cap, insisting that the player should not look at the position as a retirement fund. Coach Lawrie McKinna sought interest from Australia national football team players Ante Milicic and Simon Colosimo, and announced that he may sign more than the three under-20 players required by league rules. Early concerns for the club focussed on concerns over financial stability, but after forming a partnership with technology company Toshiba and a cash injection from local businessman John Singleton, the club's financial worries were eased. McKinna was keen to sign local player Damien Brown of Bateau Bay, formerly of the Newcastle Jets. In a decision which prompted the player to declare that he was "over the moon", Brown became the first player to sign with the club. Club chairman Lyall Gorman was pleased that a local had become a "foundation player" and part of Brown's role would be to assist with selection of younger players from the local area. By early December 2004, the club had created a steady foundation of player signings and began negotiations with former Perth Glory striker Nik Mrdja, signing him later in the month as its star attacker. Mrjda was one of the most prominent players in the last season of the National Soccer League, scoring the final goal to secure Perth Glory's finals win. The club's management was reluctant to sign a star player outside of the $1.5 million salary cap, stipulating that they "would have to contribute on the pitch and get people to come to the ground."

The Mariners' inaugural season was considered a resounding success by most; the team reached the 2006 A-League Grand Final after finishing third during the regular season. Central Coast was defeated by Sydney FC 1–0 in front of a crowd of 41,689—a competition record at the time. The Mariners also won the 2005 Pre-Season Cup, defeating Perth Glory in the final 1–0. Before the 2006–07 A-League season, the Mariners secured the services of then-Australian international Tony Vidmar from NAC Breda for two years. This was the club's first marquee signing, following the lead of Sydney FC (Dwight Yorke) and Adelaide United (Qu Shengqing). Central Coast again reached the grand final in the 2006 Pre-Season Cup, losing to Adelaide United 5–4 on penalties after the score was tied 1–1 after extra time. The Mariners then participated in the 2006–07 A-League season, but was unable to gain a spot in the final series, finishing sixth after the regular season.

Club captain Noel Spencer was released by the Mariners, then signed to participate in the Asian Champions League by Sydney FC after the 2006–07 season, and Alex Wilkinson was appointed the new captain. Only 22 years of age at the time, Wilkinson had played every possible competitive match for the Mariners up to his appointment. In February 2008, Central Coast Mariners signed an arrangement with English Football League Championship side Sheffield United. The partnership was one of several connections the Mariners made with foreign clubs; other partner clubs included Ferencváros of Hungary, Chengdu Blades of China and São Paulo of Brazil. The agreement benefits the club by providing an opportunity for the youth programme and senior side to draw from the roster of Sheffield United through transfers. The teams also formed a property development joint venture, in the hopes that Central Coast could use its share of income to expand and bolster their Mariners Youth Academy.

The 2007–08 season saw Central Coast win its first premiership on goal difference ahead of Newcastle, following a final round that began with Central Coast and three other clubs level on 31 points. The final series began with a 2–0 loss to Newcastle in the first leg of its major semi-final, but the Mariners forced the tie to extra time by holding a 2–0 lead in the second leg after 90 minutes. A 94th-minute goal by Sasho Petrovski, who had scored earlier to level the tie, gave Central Coast a 3–2 win on aggregate, putting the Mariners through to the 2008 A-League Grand Final. In a rematch with Newcastle, the Jets defeated Central Coast 1–0 in the Grand Final, which ended in controversy due to an uncalled handball against Newcastle in Central Coast Mariners penalty box during the closing seconds of the match. If called, the foul would have given Central Coast a penalty kick and a chance to equalise. As Mariners players disputed referee Mark Shield's decision, goalkeeper Danny Vuković struck Shield on the arm, resulting in an immediate sending off and later suspension. Vuković was suspended from both domestic and international competition for nine months, with an additional six-months' suspended ban; the latter period was reduced to three months on appeal. Despite further appeals, the ban was eventually confirmed by FIFA in June, to include banning the young keeper from competing at the 2008 Olympic Games. The ban lasted into October; in response, Central Coast signed former Manchester United and Australian international keeper Mark Bosnich on a seven-week contract.