[3] They played their final rugby match in February 1903, and in September 1903 the club switched codes to association football,[4] setting in motion their journey to become the modern-day Dundalk F.C.

After missing out in both the League and the City Cup by a point in 1947–48, the committee decided to invest the surplus from its transfer dealings on several professional players from Scotland and a player-coach, Ned Weir.

[32] But the new team fell short in both the Shield and the League and, despite the cup double and improved gate receipts, the additional income was not enough to cover the increase in costs.

A surplus from transfer dealings prevented a more serious financial crisis arising,[34] and despite the turnover in players, Dundalk won the Leinster Senior Cup for the first time in 1950–51.

They continued to struggle for the rest of the decade but, in contrast to their league form, they won their fourth FAI Cup with a 1–0 victory over Shamrock Rovers in the 1958 final.

[49] The new board invested heavily in both Oriel Park and the squad ahead of the 1966–67 season,[50] and signed a new player-coach, Alan Fox, from Bradford City.

[54] The following season, Oriel Park hosted European football for the first time, under newly installed floodlights, with the visit of Vasas SC of Hungary.

[55] But Fox fell out with the club's board during the trip to Budapest for the return leg, and he was released the following March, despite his side being set to retain the title.

[57] Dundalk subsequently finished as runners-up in the League, qualifying for the 1968–69 Fairs Cup, where they won a European tie for the first time with victory over DOS Utrecht.

[59] Future Ireland manager Liam Tuohy took over in the summer of 1969 and also joined the board,[60] and as a result of his managerial experience, Dundalk entered the new decade at the top of the league table.

But Tuohy was obliged to thin the squad and cut the wage bill because of the scale of the debts still hanging over the club from the redevelopment of Oriel Park,[61] and he could not build a side able to sustain a title challenge.

[64] Dundalk had to sell or release several players to survive after Tuohy left,[65] and they slid down the table with a young, inexperienced team finishing second from bottom in 1972–73.

[78] The club supported the "reorganisation" he demanded, however, and it used the funds from the sale of three players to Liverpool to invest in the squad and make ground improvements at Oriel.

[97] By the end of the season, the board was facing financial issues that threatened the club's survival—a "healthy" surplus in 1989,[98] had become a serious deficit, with income falling due to some of the lowest gate receipts in memory.

[102] Early the following season, the financial issues came to a head, and several local businessmen formed a new interim company to take the club over, saving it from bankruptcy.

But Dundalk became embroiled in a losing battle with the league's hierarchy and Kilkenny City over the latter playing an improperly registered player, which reached the High Court.

But results subsequently deteriorated and, with financial losses mounting as the 2011 season drew to a close, Matthews decided to let Foster's contract expire and relinquish control of the club.

[122] With the club in danger of insolvency during a disastrous 2012, it was taken over by local businessmen Andy Connolly and Paul Brown (owners of the team's official sponsors, Fastfix), and Dundalk subsequently managed to remain in the top-flight by defeating Waterford United in the play-off.

A draw with AZ Alkmaar in the Netherlands,[134] followed by a victory over Maccabi Tel Aviv in Tallaght Stadium, were the first points earned by an Irish club in the group stage of European competition.

[142] Despite falling 13-points behind early 2019 leaders Shamrock Rovers in April,[143] they overhauled the deficit within weeks,[144] and subsequently won the club's 14th league title, with four games to spare.

[156] The season began with a victory in the President's Cup,[157] but after a run of defeats at the start of the league campaign, both Keegan and Giovagnoli left the club.

[159] Before the season ended, the club was returned to local ownership when a consortium led by former co-owner Andy Connolly and sports technology firm STATSports agreed a takeover with Peak6.

[164] A poor start to the 2024 season resulted in O'Donnell being let go,[165] beginning a turbulent month in which he was replaced by Noel King,[166] whose tenure lasted 25 days before he resigned citing medical issues.

[179] A modified crest was reintroduced to the shirt for the 1952 FAI Cup Final, consisting of three black martlets on a white shield bearing the club name.

[172] As an association football club for the employees of the Great Northern Railway works in the town, it was 'owned' by the company and run by a management committee elected by its members.

But the co-op was unable to make the sort of investment in either the team or in Oriel Park required to bring the club back to the Premier Division.

[241] In addition to sponsorship, Oriel Park is made available for junior and schools football, and is also available for rent to private groups and clubs in other sporting codes.

[243] Players in the League of Ireland are typically signed on single or two-year contracts, resulting in large numbers of free agents at the end of each season.

[244][245] As a result, the transfer-fee inflation seen throughout European club football has not been a feature of the game in Ireland, and Dundalk have not benefited financially from player transfers since the Bosman ruling came into effect.

[277] They have played against several major names in European football such as Liverpool, Tottenham Hotspur, Arsenal, Celtic, FC Porto, PSV Eindhoven, Ajax, Red Star Belgrade, Hajduk Split, Legia Warsaw, and Zenit St Petersburg.