Context : Titan is an excellent test case for detailed studies of the scattering polarization from thick hazy atmospheres .
Accurate scattering and polarization parameters have been provided by the in situ measurements of the Cassini-Huygens landing probe .
For Earth-bound observations Titan can only be observed at a backscattering situation , where the disk-integrated polarization is close to zero .
However , with resolved imaging polarimetry a second order polarization signal along the entire limb of Titan can be measured .

Aims : We present the first limb polarization measurements of Titan , which are compared as a test to our limb polarization models .

Methods : Previously unpublished imaging polarimetry from the HST archive is presented which resolves the disk of Titan .
We determine flux-weighted averages of the limb polarization and radial limb polarization profiles , and investigate the degradation and cancelation effects in the polarization signal due to the limited spatial resolution of our observations .
Taking this into account we derive corrected values for the limb polarization in Titan .
The results are compared with limb polarization models , using atmosphere and haze scattering parameters from the literature .

Results : In the wavelength bands between 250 nm and 2 \mu m a strong limb polarization of about 2 - 7 ~ { } \% is detected with a position angle perpendicular to the limb .
The fractional polarization is highest around 1 \mu m. As a first approximation , the polarization seems to be equally strong along the entire limb .
The comparison of our data with model calculations and the literature shows that the detected polarization is compatible with expectations from previous polarimetric observations taken with Voyager 2 , Pioneer 11 , and the Huygens probe .

Conclusions : Our results indicate that ground-based monitoring measurements of the limb-polarization of Titan could be useful for investigating local haze properties and the impact of short-term and seasonal variations of the hazy atmosphere of Titan .
Planets with hazy atmospheres similar to Titan are particularly good candidates for detection with the polarimetric mode of the upcoming planet finder instrument at the VLT .
Therefore , a good knowledge of the polarization properties of Titan is also important for the search and investigation of extra-solar planets .