Ticket for one trip on Paris Metro?

Paper tickets are still available. You should be able to buy one from a machine, but I know that sometimes people with American credit cards have difficulties. Hope someone with more recent experience of trying to use an American card will chime in.

You don't happen to have a two-euro coin left over from an earlier trip ? (One ticket costs €1.90.)

I was just there in May. You can buy a single, double, etc. ticket by a machine. It has a tricky to use rolling bar to select the option you want. I bought 2 single use tickets. They were paper as were the carnet (10 tickets) I bought 3 days earlier. Paper tickets still very much in use!

I did buy my tickets with coins.

Thanks to all who posted - I do have euro and will have coins. Very reassuring - I need to read the RATP site more carefully, apparently! I'll be back to Paris later in the trip and will have the energy to buy a pass or e-carnet at that point. Merci beaucoup.

metro machines take US cards when they ask for the pin just ignore it and continue -- works at least up to 75 Euros.

The only time my credit card was denied on the whole trip was at the Pyramides station (and of course the booth was unmanned at that time). I would find one that works and load up a couple of trips ahead.

I could not find carnets, which they really seem to be phasing out. But you could still order paper tickets. The limit per order was 9 tickets, although you could place more than one order per transaction.

Currently in Paris, arrived on June 15th . My family purchased the paper tickets from staffed metro stops and have been using them to go to the Orsay, Louvre, Monmartre, etc. The metro entrance booths still take paper tickets and/or Navigo cards. One of our tour guides stated that they extended the paper tickets till October (but I can't confirm that).

I bought a fistful of little paper tickets back in January at a machine with no problem, as Jane noted when the vending machine hesitates and asks for a pin just wait and it will probably process the transaction

Once again, I thank fellow travellers for all these helpful replies!