Lemannville is an unincorporated community and census-designated place in Ascension and St. James parishes, Louisiana, United States. It was first listed as a CDP in the 2010 Census. Per the 2020 census, the population was 695.

Lemannville is located on the west bank of the Mississippi River along Louisiana Highway 18, 6 miles (10 km) east of Donaldsonville and 60 miles (100 km) west of New Orleans.

Historical population

Census	Pop.	Note	%±
2010	860		—
2020	695		−19.2%
U.S. Decennial Census 2010 2020

Lemannville CDP, Louisiana – Racial and ethnic composition
Note: the US Census treats Hispanic/Latino as an ethnic category. This table excludes Latinos from the racial categories and assigns them to a separate category. Hispanics/Latinos may be of any race.

Race / Ethnicity (NH = Non-Hispanic)	Pop 2010	Pop 2020	% 2010	% 2020
White alone (NH)	250	135	29.07%	19.42%
Black or African American alone (NH)	599	533	69.65%	76.69%
Native American or Alaska Native alone (NH)	0	1	0.00%	0.14%
Asian alone (NH)	0	0	0.00%	0.00%
Pacific Islander alone (NH)	0	0	0.00%	0.00%
Other race alone (NH)	0	0	0.00%	0.00%
Mixed race or Multiracial (NH)	2	8	0.23%	1.15%
Hispanic or Latino (any race)	9	18	1.05%	2.59%
Total	860	695	100.00%	100.00%