How do you say this is my grandfather in French?

There are a few ways to say "This is my grandfather" in French, depending on the context and level of formality:

Formal:

* "Ceci est mon grand-père." (This is my grandfather.) - This is the most formal way to say it.

* "Voici mon grand-père." (Here is my grandfather.) - This is also formal, but slightly more direct than "Ceci est..."

Informal:

* "C'est mon grand-père." (This is my grandfather.) - This is the most common and informal way to say it.

* "Voilà mon grand-père." (There's my grandfather.) - This is also informal and emphasizes the presence of the grandfather.

You can also use the possessive pronoun "mon" (my) before "grand-père" to emphasize the relationship:

* "Mon grand-père." (My grandfather.)

The best choice will depend on the situation and your relationship with the person you are talking to.