Linfield overcame Sammarinese champions La Fiorita in the first round of Champions League qualifying, but now they face a much sterner challenge against a club from a league ranked 20 places higher. We ask...
Who are Glasgow Celtic?
Celtic are Scotland's second most successful football club and the first British club ever to lift the European Cup, back in 1967.
The club, based in the Parkhead area of Glasgow, have won the league title 48 times, 37 Scottish cups and the Scottish League Cup on 17 occasions – a record bettered only by rivals Rangers.
Celtic are yet to kick off their league season this year, however they have won the Scottish league for the last six years in succession.
Those titles have largely come in the absence of Glasgow Rangers, who were liquidated in 2012 and re-entered the league in the fourth tier.
This has prompted Rangers chairman Dave King to suggest that four of those titles don't count as Rangers weren't in the league to compete for them, however the club's recent Europa League defeat to Progres Niederkorn means this view can safely be discounted.
Last season saw the club achieve their palmares: an unbeaten season (the club's first since 1897-98) and a treble of league, cup and league cup triumphs under manager Brendan Rodgers.
While Celtic might not be a hugely familiar name in Ireland, the club has tremendous European pedigree that stands up against some of the continent's best sides.
1967 saw the immortalisation of the famed 'Lisbon Lions,' so called as Jock Stein's charges led the club to a 2-1 victory over Inter Milan in the European Cup final in the Portuguese capital.
That side contained such as Billy McNeill, Jimmy Johnstone, Tommy Gemmill and Irishman Charlie Gallagher.
That was the first of three European finals the club reached – they returned to the European Cup final three years later, losing to Feyenoord in Milan, and the UEFA Cup final in 2003.
The latter occasion saw a Celtic side managed by current Republic of Ireland boss Martin O'Neill lose narrowly to Jose Mourinho's Porto, a year before the Portuguese won the Champions League.
More recently, the club have managed a number of impressive results in Europe, including a 2-1 win over holders Barcelona in 2012 as well as home and away draws with Manchester City last year.
Who will League of Ireland fans recognise?
Republic of Ireland fans will certainly recognise new signing Jonny Hayes, who made the move to Celtic Park in the off-season from last season's runners-up Aberdeen.
Captain Scott Brown will also be a familiar face for Ireland fans, having twice faced the Boys in Green during Scotland's unsuccessful Euro 2016 qualifying campaign, although the Scots took four points from those two games.
Right-back Mikael Lustig was part of the Sweden team that held Ireland to a 1-1 draw at the finals in Paris, and he was also part of the side that won 2-1 at Lansdown Road in one of Giovanni Trapattoni's final games in charge.
The majority of players will also be familiar to Shamrock Rovers fans, who watched a strong Celtic side defeat their youth team in Tallaght last Saturday. The game was watched by almost 7,000, the majority of whom had travelled from Scotland to support the visitors, which shows just how dedicated the club's fanbase is.