- Dendrobium racemosum – "rattail orchid"
- Dendrobium rachmatii
- Dendrobium radians
- Dendrobium ramificans
- Dendrobium ramosii – Ramos' Dendrobium
- Dendrobium rantii
- Dendrobium rappardii
- Dendrobium rariflorum
- Dendrobium rarum
- Dendrobium rechingerorum
- Dendrobium recurvilabre
- Dendrobium reflexibarbatulum
- Dendrobium reflexitepalum
- Dendrobium refractum
- Dendrobium regium
- Dendrobium reineckei
- Dendrobium reniforme
- Dendrobium rennellii – Rennell Dendrobium
- Dendrobium revolutum
- Dendrobium rex (formerly D. speciosum var. grandiflorum)
- Dendrobium rhabdoglossum
- Dendrobium rhodobalion
- Dendrobium rhodocentrum
- Dendrobium rhodostele
- Dendrobium rhodostictum – Red-spotted Dendrobium
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- Dendrobium rhombopetalum
- Dendrobium rhytidothece
- Dendrobium rigidifolium
- Dendrobium rigidum
- Dendrobium rindjaniense
- Dendrobium riparium
- Dendrobium roseicolor
- Dendrobium roseipes
- Dendrobium rosellum
- Dendrobium roseoflavidum
- Dendrobium roseonervatum
- Dendrobium roseostriatum
- Dendrobium rubropictum
- Dendrobium ruckeri
- Dendrobium ruginosum
- Dendrobium rugosum
- Dendrobium rugulosum
- Dendrobium rupestre
- Dendrobium rupicolum
- Dendrobium ruppianum – Small Demon Orchid (formerly D. fusiforme)
- Dendrobium × ruppiosum (D. ruppianum × D. speciosum)
- Dendrobium rutriferum
- Dendrobium ruttenii
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