What is the best London Underground pass for a week?

Just use your tap credit or debit card.

Oyster card…lots of info on-line if you Google London Underground.

I've never heard of a pass for the tube: https://tfl.gov.uk/fares/contactless-and-oyster-account. If you don't have an Oyster card you might be able to use a contactless credit card.

I think language and expected meaning may be causing some misunderstanding here.
Most people pay as they go with either a preloaded Oyster Card or Tapping in with a contactless credit card.
There is something called a travelcard, but it is questionable whether it would really save you money. Here is a link to the page that describes it.
https://tfl.gov.uk/fares/how-to-pay-and-where-to-buy-tickets-and-oyster/travelcards-and-group-tickets?intcmp=54706

Transport for London (TFL) offers a 7 day Travelcard:

https://tfl.gov.uk/fares/how-to-pay-and-where-to-buy-tickets-and-oyster/travelcards-and-group-tickets#on-this-page-0

Addendum: Carol and I posted at the same time.

There is a daily cap on the tube/buses. You have to decide if it is cheaper for you to just use tap in and out or to get a travel card.

I've never heard of a pass for the tube

It's called a Travelcard.

The answer is never simple. It depends on the days of the week you are there as to whether a weekly cap on Oyster or Contactless fares is the best, or a Travelcard.

It also depends if the only time you will be going outside the central area (Zones 1 and 2) is to and from Heathrow, or if you are doing other visits outside the central area eg- to places like Greenwich, Hampton Court, Richmond or Kew to give a few examples.

Also if you are travelling to/from Heathrow by tube or by the Elizabeth Line.

Also if you are doing one or two tube journeys a day, or multiple journeys.

There isn't a one size fits all "best answer".

It is very easy to get caught in doing complex high level maths. In truth the difference between Oyster or contactless capping and travelcards, or all zone or just Zone 1 and 2 cap (if doing a number of trips to outer zones) is so relatively small (in the overall cost of the vacation) it just isn't worth all the maths.

Sometimes the highest priced option is worth the flexibility and not having to think about zones.

People will make very pejorative comments on this forum about not using an Oyster Card, you must use contactless. At the end of the day the Oyster Card costs £7 (2 take out coffees), and topping it up is easy. If you prefer to use an Oyster card to using contactless bank cards do so.

Travelcards may save you some money in a very specific use case if you have a daily commute. Otherwise, not worth the extra step of buying one these days.

Just use a credit card and tap into and out of stations. Forget Oyster or travelcards. You get a daily maximum billed to your card if you use it a lot in one day. WAY easier. The London transport system, and UK train system, is made by insane people - you will never get to the bottom of it - designed to take advantage of us tourists. Not meaning to think badly of people with "neuro" differences.

How is a system which allows you to use a contactless card or phone or smart watch pay to cover all your public transport in the city and will calculate the cheapest fare for the journeys you make in a day exploiting tourists? You will pay the same as everyone else.

Also the daily fare cap, whether you use Oyster, a form of contactless payment, or Travelcard is essentially the same. There will at worst be a few pence difference.
Oyster or contactless is always the same fare, same cap, same everything, on the main zones 1 to 6.
The same is true on main line trains.
Everyone is subject to the same fare structure. There is no two tier structure. It really is up to the individual citizen or tourist to inform themselves. If you buy rail tickets from many of the train companies websites or machines they will actually prompt you if there is a lower fare available.

I think everyone can agree that the national rail system is a complete mess with a mind boggling number of different ticket options.

However, Transport for London is actually great and very user friendly.

Especially if you know how to use the Hopper Fare. You have 60 minutes... The clock is starting...