Grimisuat is a municipality in the district of Sion in the canton of Valais in Switzerland.
Grimisuat is first mentioned around 1001-1100 as Grimisoch. The municipality was formerly known by its unknown name Grimslen, however, that name is no longer used.
Grimisuat has an area, , of . Of this area, or 47.3% is used for agricultural purposes, while or 22.3% is forested. Of the rest of the land, or 27.7% is settled (buildings or roads), or 0.9% is either rivers or lakes and or 2.0% is unproductive land.
Of the built up area, housing and buildings made up 19.6% and transportation infrastructure made up 5.2%. while parks, green belts and sports fields made up 1.4%. Out of the forested land, 13.5% of the total land area is heavily forested and 8.8% is covered with orchards or small clusters of trees. Of the agricultural land, 0.9% is used for growing crops and 18.0% is pastures, while 28.4% is used for orchards or vine crops. Of the water in the municipality, 0.2% is in lakes and 0.7% is in rivers and streams.
The municipality is located in the Sion district, on the right bank of the Rhone river. It consists of the village of Grimisuat and the hamlets of Comera and Les Combes.
The blazon of the municipal coat of arms is Gules, a Fleur-de-lys Argent between in chief two Mullets of Six Or.
Grimisuat has a population () of . , 11.5% of the population are resident foreign nationals. Over the last 10 years (2000–2010 ) the population has changed at a rate of 23.6%. It has changed at a rate of 13.9% due to migration and at a rate of 7.7% due to births and deaths.
Most of the population () speaks French (2,128 or 91.3%) as their first language, German is the second most common (95 or 4.1%) and Portuguese is the third (42 or 1.8%). There are 25 people who speak Italian.
the population was 51.5% male and 48.5% female. The population was made up of 1,258 Swiss men (45.1% of the population) and 177 (6.4%) non-Swiss men. There were 1,176 Swiss women (42.2%) and 176 (6.3%) non-Swiss women. Of the population in the municipality, 946 or about 40.