How much is a ticket from Madrid to Lisbon?

The cheapest price found today is $19.

When is it cheaper to fly?

Cheapest month is September — from $19.

Cheapest today — $19. Below is what booking services offer.

Departure	Airline	Stops	Price
Sep 2	Ryanair	direct	$19	View
Sep 6	Ryanair	direct	$22	View
Sep 30	Ryanair	direct	$23	View
Sep 8	Ryanair	direct	$24	View
Sep 9	Ryanair	direct	$24	View
Oct 7	Ryanair	direct	$24	View
Sep 29	Ryanair	direct	$26	View
Aug 25	Ryanair	direct	$27	View
Sep 16	Ryanair	direct	$29	View
Aug 26	Ryanair	direct	$29	View

How much is a ticket from Madrid to Lisbon?: The cheapest price found today is $19.
When is it cheaper to fly?: Cheapest month is September — from $19.

Links to booking services are affiliate links. The price stays the same for you.