Upvote:7
Considering your edit (liberation of the north-eastern border): I would say March 19th 1945 after Lauterbourg was taken back in Alsace. You may also consider the city of Saorge, at the Italian border, liberated in April 24th.
But I don't think it makes so much sense to try to find a definitive day of the French liberation, because of the "pockets" which resisted even after the German capitulation. History tends to focus on the liberation of major cities and the scale of the battle. In this respect, Colmar (Feb 2nd) in Alsace is often cited as the last major battle on French territory. Also remember that the French Army (with the Allies) crossed the Rhine before these "pockets" were liberated on its own territory.
Upvote:26
The answer is surprisingly difficult to find on Wikipedia. I persisted in searching and finally found this:
German military administration in occupied France during World War II
The Liberation of France was the result of the Allied operations Overlord and Dragoon in the summer of 1944. Most of France was liberated by September 1944. Some of the heavily fortified French Atlantic coast submarine bases remained stay-behind "fortresses" until the German capitulation in May 1945.
After the liberation of Brest on 19 September 1944, the Allies decided to lay siege to the remaining pockets and not to take them by force. Only Royan was subsequently assaulted, falling to French forces on 20 April 1945 during the siege of La Rochelle, which did not itself capitulate until 8 May.
The remaining pockets were:
Channel Islands (surrendered 9 May 1945)
Dunkirk (besieged since 15 September, surrendered 9 May 1945)
Lorient (besieged since 12 August, surrendered 10 May 1945)
Saint-Nazaire (besieged since 27 August, surrendered 11 May 1945)
So it seems that metropolitan France was not fully freed of belligerent German forces until 11th May 1945, 3 days after the Armistice.
On the North-Eastern front, the last major battle was in Colmar, Alsace:
The battle lasted 20 January – 9 February 1945 , with the liberation of Colmar on Feb. 2nd and the collapse of the pocket on Feb. 9th.
We can also mention Sarreguemines, a small town in the Moselle departement near the German border.
On December 21–23 1944, the 44th Infantry Division (United States) threw back three attempts by the Germans to cross the Blies River. An aggressive defense of the Sarreguemines area was continued throughout February and most of March 1945.
The following articles in the French wikipedia cover exactly the full scope of the question: