I'm inclined to close as "won't fix". Titles are not considered data content and thus not taken into account for legend placement. The same would hold true for axis labels.

If you want to place text inside the Axes, I propose to use plt.text() instead, e.g.

plt.text(0.5, 0.9, 'Just a very long title 1234567890', ha="center", transform=plt.gca().transAxes)

we can do many things for this issue 1 is that we can position the legend outside the fox here is the code for this I have used
{ bbox_to_anchor } for this

`
import matplotlib.pyplot as plt

plt.close('all')
plt.plot((1, 2, 3), label='Just a very long legend')
plt.title('Just a very long title 1234567890', y=0.9)
plt.legend(loc='upper center', bbox_to_anchor=(0.5, -0.1), ncol=1)
plt.show()

`

Agree with @timhoffm that this is likely a won't fix. If the user wants to place the title in such a non-default location they can also place the legend manually to use a bbox as suggested by @Shivangbijalwan

Thank you all for your answers. My use case is inside a 2-by-4 subplot, where each subplot has a different legend. For this reason, placing the legend outside the axes is not an option in this case. I'll try using plt.text as suggested by @timhoffm .

Given that y is a documented parameter of plt.title, shouldn't the documentation mention that playing with it won't guarantee that plt.leged(loc='best') will do its job?

Given that y is a documented parameter of plt.title, shouldn't the documentation mention that playing with it won't guarantee that plt.leged(loc='best') will do its job?

I'd go the other way, and in legend document that best only works for artists added to the axes, not axes labels.

I agree that more detailed documentation of the loc="best" is the way to improve here.