The first Horsham Football Club was founded in 1871, though its existence largely depended upon enough players being available to form a side.
In 1881 the club was firmly re-established and, in September 1882, helped found the Sussex County Football Association before becoming became founder members of the West Sussex Senior League in 1896, winning the championship in 1899/00, 1900/01 and 1901/02, and claiming the Royal Irish Rifles Cup in 1900. Having initially played at both Hurst Park and Springfield Park, the club secured Queen Street as its permanent home in 1904 but some lean form over the ensuing years saw Horsham overlooked when the Sussex County League was created in 1920 and it wasn’t until their fourth West Sussex Senior League triumph in 1925/26 that they were invited to make the step up. The 1930s was a golden era for the club and the County League was won six times during the decade, Horsham regularly scoring over one hundred goals a season. Cup competitions provided more silverware with the Sussex RUR Cup (seven times) and the Sussex Senior Cup (twice) both finding their way back to Queen Street before the outbreak of war. When peace returned to the world, Horsham won the first post-war title in 1947, the RUR Cup in 1946, 1949 and 1951, and the Sussex Senior Cup in 1950.
In 1947/48 the club reached the First Round Proper of the FA Cup for the first time, taking a first minute lead against Notts County before losing 9-1. Having had successive applications to join the Athenian League rejected, the club changed tack and successfully applied to become members of the Metropolitan League that included the ’A’ sides of top Football League clubs, the reserve sides of ‘professional’ non-league clubs and a few amateur teams and Horsham confounded common opinion by winning the championship at the first attempt. However, over the years the league became stronger and stronger and eventually the amateur clubs struggled to make any impact at all and Horsham finished the 1956/57 season at the foot of the table, having already decided to quit the league in favour of the Corinthian League where they began a period of consistent progress, finishing thirteenth, ninth, eighth and fifth before their best ever season in 1961/62 when third place was achieved.
Following a mass exodus of players, Horsham were forced to rebuild with a young, local team that would peak at fourth place in 1964/65 only to become the first Horsham side ever to be relegated the following season. Under coach Pat Tobin, the team was rebuilt once more and this reaped dividends in 1966/67 when the club once again reached the First Round Proper of the FA Cup, with the visit of Swindon Town drawing a record 7,134 crowd to Queen Street. Despite this achievement this was a frustrating period of near misses for the club who finished third, third and fifth and suffered three consecutive defeats in the final of the Sussex Senior Cup. By now nicknamed the Hornets, following a supporters’ competition, the club appointed Roy Osborne as their new manager and the change brought immediate success with the championship of Division Two achieved in 1969/70, the Division One title in 1972/73, and the Sussex Senior Cup in 1972. Instead of taking their place in the Athenian League Premier Division, Horsham became members of the Isthmian League when that competition expanded to two divisions in 1973/74, finishing eighth in its first season and rounding the season off in style by winning the Sussex Senior Cup. Now under the guidance of Tony Elkins-Green, 1976/77 saw the Hornets finish in a best ever sixth place but financial problems threatened the club’s very survival and only the dedicated work of chairman Frank King saw the club saved from bankruptcy and dissolution although it couldn’t prevent a young amateur team from finishing bottom of Division One in 1979/80 and the club was relegated to the new Division Two. Horsham endured some dark times under numerous managers in the 1980s, finishing bottom of the league in 1983/84 and 1989/90, when only a successful relegation play-off against Letchworth Garden City maintained the club’s Isthmian status. Progress was made under the management of Peter Evans from 1990, during which time the club reached the final qualifying round of the FA Cup, though under his replacement, John Yems, Horsham once again propped up the entire league in 1993/4 leading to the appointment of former captain Mark Dunk as manager. He led his side to the Division Three championship in 1995/96, narrowly missing out on a second successive promotion before departing in 1997.
Three years of lower mid-table obscurity followed before former Crawley Town boss John Maggs took over as manager in January 2000, taking a struggling side out of the relegation zone to Division Two runners-up in three seasons and a promotion play-off final appearance in 2004/05. Promotion to the Premier Division was achieved the following season with another runners-up finish and the club went on to establish itself as a consistent performer, even challenging for a place in Conference South in 2007/8 before ending up eleventh. The Hornets made history in 2007/08 by reaching the second round proper of the FA Cup and taking eventual League One champions Swansea City to a replay, with both matches shown live on Sky TV. Having sold their ground for redevelopment at the end of the season, Horsham played at Worthing during 2008/09 and again reached the fourth Qualifying Round of the FA Cup where they took Conference side Stevenage Borough to a replay before ending an injury-ravaged year in thirteenth place. Season 2009/10 saw a return to Horsham, entering into a groundshare agreement with their old neighbours Horsham YMCA as their quest for a new ground continued, but fortunes were on the wane and an acute overhaul of the club’s finances in 2011 resulted in the departure of Maggs after eleven years. A turbulent 2011/12 found the club under three different managers, with Simon Colbran ultimately unable to prevent the side from returning to Division One South. A season of stability followed, with the Hornets ending the campaign in fifteenth and claiming the Brighton Charity Cup for a second successive season. The club entered a new chapter in November 2013 when, following Colbran’s departure to Crowborough Athletic, long-serving player Gary Charman was appointed as first team manager. Charman steered the club to 16th place but a poor run of results the following season led to him being replaced by two more former players, Anthony Storey and Cliff Cant, in January 2015. Despite some impressive initial results, the pair were unable to save the club from relegation so former East Preston manager Dominic di Paola was appointed towards the end of the campaign with a view to rebuilding a side capable of competing in the Sussex County League for the first time since 1951.
A season long battle with Eastbourne Town followed before Horsham took the title by eleven points to secure a record-equalling eighth County League title, thus securing an immediate return to the Isthmian League for season 2016/17. During the 2015/16 campaign, the club recorded a club record 97 points whilst conceding the fewest goals in their history (22).