The man, brandishing a sawn-off shotgun and a knife, tied up and killed the woman who worked at the home in the village of Montferrier-sur-Lez near the city of Montpellier, a prosecutor said.
More than 70 men and women, most of whom served as missionaries in Africa, live at the home.
Armed police searched the building but believe the man fled, sources close to the police operation said, and a large-scale police operation was under way to find the unidentified attacker.
Investigators so far had no evidence to suggest the attack was terror-related at a time when France remains under a state of emergency after a number of Islamist atrocities, including the murder of an elderly Catholic priest in July.
"For the time being, there is only one victim," Montpellier prosecutor Christophe Barret told AFP. "For the moment there is no particular evidence about the motive for this crime."
"Nothing is pointing towards the motive" of the killer, he added.
The man was not known to authorities.
Many of the residents require assistance to walk, he said.
The secretary general of the French Bishops' Conference, Olivier Ribadeau Dumas, said in a Twitter message: "Our prayers tonight go to the woman who lost her life in this attack on a retirement home."
Around two hours after the attacker burst into the home, more than a dozen police and emergency vehicles lined the roads near the home while police set up roadblocks to check vehicles passing through the area.
France is under a state of emergency that gives security forces enhanced powers of surveillance and arrest.
Islamist extremists have carried out three large-scale attacks in France since January 2015, when gunmen targeted the Charlie Hebdo satirical magazine and a Jewish supermarket.
Disclaimer: No Business Standard Journalist was involved in creation of this content
You’ve reached your limit of 5 free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Access to Exclusive Premium Stories
Over 30 subscriber-only stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app