Racing 92's Champions Cup semi-final against Saracens at La Defense Arena on Saturday will take place in front of 1,000 fans, following a tightening of coronavirus restrictions in France.
The club has been obliged to cut the size of the crowd from 5,000 as the number of coronavirus cases in Paris and its suburbs passed a key threshold of 150 cases per 100,000.
Fans have been allowed into French rugby grounds under certain conditions since the start of the new season in early September.
Initially, regional authorities were able to exempt grounds from a government-set capacity limit of 5,000 based on the local health situation and clubs' own sanitary measures - but more stringent regulations have been brought in as the health situation in France changed for the worse.
On Wednesday, France's Health Minister Olivier Veran announced further restrictions where virus rates were increasing fastest, including the maximum limit of 1,000 people at organised gatherings, such as professional sports events; a ban on local festivals; the closure of sports halls and gymnasiums where 'wearing a mask is impossible or complex'; a ban on informal gatherings of more than 10 people in public spaces; and the partial closure of bars.
The next threshold - when even stricter measures take effect - is 250 cases per 100,000 and coronavirus patients occupying 30% of a region's available intensive care beds.
To date Aix, Marseille and Guadeloupe are at the higher level of health measures.
According to the club, La Defense Arena - which hosts concerts and other events as well as Racing 92's home matches - has lost €28m in operating revenue since lockdown in March, and would continue to lose between €115,000 and €120,000 for every game at which the crowd is limited to 1,000.