The ever-increasing traffic has been driving the demand for compact, high-speed, and low-power-consumption optical transmitters. Thin-film lithium niobite (TFLN) platforms have emerged as promising photonic integrated solutions for next-generation optical transmitters. In this study, we demonstrated the first widely tunable optical transmitter based on a butt-coupling a TFLN modulator with an electrically pumped tunable laser. The tunable laser exhibited a side-mode suppression ratio of > 60 dB, linewidth of 475 kHz, and wavelength-tuning range of over 40 nm. The TFLN modulator presented a voltage-length product of 2.9 V·cm and an electro-optic response of 1.5 dB roll-off at 50 GHz. The optical transmitter support data rate was as high as 160 Gb/s.