The nymphs of nine species of baetid mayflies from Sri Lanka are described in detail. These include Baetis frequentus sp.n., B. acceptus sp.n., B. conservatus sp.n., B. collinus sp.n., B. geminatus sp.n., B. pulchellus sp.n., B. ordinatus sp.n., and Procloeon regularum sp.n. A single nymph of Cloeon appears closely related to Cloeon bimaculatum Eaton. The first four species mentioned do not fit in any known species-group. Baetis geminatus sp.n. and B. pulchellus sp.n. are associated with the Oriental molawinensis species-group (which corresponds to the European atrebatinus species-group and to the North American propinquus species-group). The sumigarensis sub-group is proposed within the molawinensis species-group. The nymphs described herein are the first nymphs to be described in the family Baetidae from Sri Lanka. The genus Procloeon is recorded from the Oriental Region for the first time. A key to the baetid nymphs of Sri Lanka is included.