Suiko is a Japanese electronic instrument maker best known for a small line of synthesizers built around the sounds and playing conventions of traditional Japanese music. The brand's instruments were produced in limited quantities beginning in the 1980s, originally aimed at a niche audience of koto students, traditional-music teachers, and performers who used them to accompany poetry and vocal recitation. The product family is identified by ST-series model numbers, including the ST-10, ST-20, ST-30, ST-40, ST-50, ST-60, ST-70, ST-80, and ST-100.

The most widely known model is the Suiko ST-50, a multi-sound koto synthesizer with a two-row button keyboard laid out for easy glissando playing in the style of a koto. It includes presets for Japanese instruments such as koto and shakuhachi alongside oboe, strings, and chorus voices, plus a percussion mode stocked with traditional drums. Hardware features include built-in stereo speakers, sustain and pedal jacks, octave shift, vibrato and bend controls, mono/poly switching, an auto-chord button that produces stylized Japanese chord voicings, and a dedicated trill switch that imitates a koto ornament.

Suiko instruments were expensive when new and produced in small numbers for a specialized domestic market, which has made them difficult to find even in Japan. They have since attracted interest from collectors, sound designers, and experimental electronic musicians drawn to their unusual interface and distinctive sample set, with the ST-50 in particular surfacing in demos and feature pieces on outlets such as Reverb and Synthtopia.

Suiko has 7 products cataloged on Equipboard, including Synthesizers.