Liina Olmaru (often credited as Liina-Riin Olmaru; born April 11, 1967) is an Estonian stage, radio, television, and film actress.

Liina-Riin Olmaru was born in 1967 in Tallinn to actors Rein Olmaru and Linda Olmaru (née Kuusmaa). She has three siblings. In 1985, she graduated from Rakvere 1st Secondary School (now, Rakvere Gymnasium). In 1989, she graduated from the Vanemuine theatre teaching studio in Tartu.

Olmaru's interest in theology led her to study at the Institute of Theology of the Estonian Evangelical Lutheran Church, graduating from the institute's Pedagogy Department in 1996.

Liina Omaru's first significant television appearances came in 1995 as the character Virve in the Eesti Televisioon (ETV) dramatic television series Wikmani poised, based on the 1988 novel of the same name penned by Estonian author Jaan Kross. In 2007, she appeared in the role of Piret on the Swedish crime drama television series Tusenbröder; the previous year she had played the same character in the Erik Leijonborg directed feature film adaptation of the series titled Tusenbröder - Återkomsten. Also in 2007, she made an appearance on the ETV crime drama series Ohtlik lend as the character Anne Kulik.

In 2008, she played the role of Elfriede Kallaste in nine episodes of the ETV historical drama television mini-series Tuulepealne maa, which was a twelve-part mini-series chronicling the early 20th-century history of Estonia; its birth as a country, the Estonian War of Independence, post-war life throughout 1920 up to 1941 and World War II.

Other television appearances include a small role as Barbi on the Kanal 2 drama series Pilvede all in 2010; and as Ireen in Klass - Elu pärast, which was a 2010 television mini-series follow-up to Klass, the Ilmar Raag directed 2007 feature film about school bullying and violence.

Liina Olmaru has also appeared in a number of memorable radio theatre plays, including the role of Enenken Üüve in Ekke Moor in 2002, as Virve Adamson in Madis Kõiv's Üks teine lugu in 2003, and as Linda Vilde in Heidi Sarapuu's Tervist, härra Vilde! in 2015.

Olmaru's first feature film role was in the 2003 Russian language romantic drama Yantarnye krylya, directed by Andrey Razenkov. This was followed by the role of Piret in the 2006 Swedish language crime thriller Tusenbröder - Återkomsten, directed by Erik Leijonborg for Moviola Film och Television AB and Nordisk Film. The following year she appeared as Veera in the Estonian dramatic film short Öö, directed by Jaanis Valk.

Liina Olmaru married actor Indrek Sammul in 1998. The couple have three adopted children; two sons and a daughter. They currently reside in Tallinn.