Toivo Ilmari Hannikainen (19 October 1892, in Jyväskylä – 25 July 1955, in Kuhmoinen) was a Finnish composer and virtuoso pianist.
After studying at the University of Helsinki (1911–14), he became a pupil of Franz Schreker at the Musikakademie in Vienna, and continued his studies with Alexander Siloti in Saint Petersburg (1915–17) and with Alfred Cortot in Paris (1919).
Returning to Finland, he taught piano at the Helsinki Conservatory and later gained a Professorship at the Sibelius Academy.
Hannikainen steered Finnish classical music from late Romanticism towards Impressionism.
Some musical colleagues, like Aarre Merikanto, considered his death a suicide.