Nikita Parris marked her home debut with an early goal as Arsenal beat Slavia Prague 3-0 in the first leg of their Women's Champions League qualifier at Meadow Park.
The summer signing from Lyon headed the opening goal after only 94 seconds, before captain Kim Little doubled the advantage from the penalty spot just after the half-hour mark and substitute Vivianne Miedema sealed victory with a fine chip.
Republic of Ireland international Katie McCabe was part of the Arsenal starting side.
The Londoners, who beat Slavia 13-2 on aggregate in the Champions League two years ago, will look to complete the job in the second leg on 9 September.
Manchester City still have work to do in their tie after conceding a late goal to draw 1-1 against Real Madrid.
Caroline Weir's strike early in the second half looked to have given City a first-leg advantage at the Estadio Alfredo Di Stefano but Kenti Robles' injury-time effort levelled things up for the Spanish side.