The somatic chromosome numbers and karyotype of Thai Fimbristylis species were determined from root tips. The chromosomecounts and karyotype formulae are 2n=20 (16m+4sm) for F. argentea, 2n=26 (2M+10m+14sm) for F. dichotoma, 2n=4 (2m+2sm) for F. pubisquama, 2n=10 (6m+4sm) for F. insignis, 2n=10 (8m+2sm) for F. eragrostis, F. fusca, F. littoralis, F. ovata and F. umbellaris, and 2n=10 (4m+6sm) for F. thomsonii. Chromosome numbers of F. eragrostis, F. fusca, F. insignis, F. pubisquama and F. thomsoniiare newly reported. The present study determined several karyotype asymmetry values. In addition, correlation between the karyotype asymmetry values were shown in this study. The dispersion diagram was found based on A1 and A2. The Stebbins categories of Fimbristylis investigated taxa were 3A, 4A and 4B.